When Saan was born, however, we had a Baby Bjorn (mostly harmless but pretty uncomfortable for parent and baby, not to mention bulky and of limited usefulness) and a big pile of padding that masqueraded as a sling (sigh...). Naively, I believed that modern technology and progress must have created a better baby carrier than the traditional carriers used by generations of peoples across the world. I was surprised to discover that the most comfortable, versatile, useful, and altogether appealing carrier around (well, in my humble opinion!) is a big piece of cloth! "Sash" or rebozo carriers are used in many, many different cultures in many, many different ways.
This particular rebozo (made by Ellaroo) was hand-woven in Guatemala. Jovan and I find the fabric absolutely lovely and feel so chic walking down the street wrapped up in it! Also, Saan is quite smitten with it (and has been since she was about four months old, when we got ours) and it is now one of her favorite toys: she drags it behind her around the house and wraps it around herself like a little mummy. We know it comes with pretty limited instructions, though, and we really had to learn to use it on our own, so we did up a page of our own instructions that we hope helps you figure it out quickly, gives you a good idea of its flexibility and range, and maybe even inspires you to make up your own ties and carries!

Here my top
hand is holding the inner rail and my bottom hand is holding the outer
rail.

First cross the horizontal strap over the vertical strap.

Then
pass it back under the vertical strap and up towards your opposite
shoulder.

Then pass it back under the vertical strap.

And
then back over the vertical strap and through the loop you've just
made. Yay! You're done!

To tighten the sailor's knot, pull on the vertical strap and its tail.

To
loosen it, pull on the loop. Adjust by sliding the knot up and down
the vertical strap.
This all probably sounds very complicated, but it takes me all of 5 seconds to tie the rebozo on with a sailor's knot, and it's really handy to be able to adjust it (I suck at getting the pouch the right size from the beginning!). The fabric of the Ellaroo rebozo is "grippy" enough that this is a very secure knot. It doesn't work well on very "slippery" fabrics, though.
A note about comfort (yours, not the baby's!): it may take you some practice before your ties are routinely comfortable and secure, and even more time before you always get them the right size on the first try. If you find the fabric is hurting your shoulder, make sure it is well spread over your shoulder and upper arm and that it isn't twisted on your back. This will distribute the baby's weight over the largest possible surface area. It's actually possible to spread this particular rebozo so that it covers nearly all of your back and your whole shoulder and upper arm. This isn't particularly good for arm mobility, but it's GREAT for comfort. Find your own balance.
If you find there's a "pressure point" on your shoulder, try to spread the fabric in that area a little better---it may just be a bunched up bit of fabric. Make sure the sling isn't riding up your neck and that the baby isn't riding too low on your body---she should be between your chest and bellybutton---much lower than that and your back will get really tired.

First, fold the rebozo in half length-wise (so you
are left with a long, narrow piece of fabric).

Hold
the fabric across your back with then fold down and drape one end over
your shoulder. Bring the other end around the other side of your
body. Make sure the fabric is not twisted and is spread well across
your back; this helps distribute the baby's weight well.

Tie the two ends in front of you, just below your
shoulder.

Make
sure to tie the rails of the fabric somewhat tighter than the
fold---this makes a secure pouch for the baby.
You will probably have to experiment a little bit to figure out how big to make the pouch, but tighter is generally better (easier on your back, more secure for the baby). I find that when I pull all the fabric of a comfortable tie down, it doesn't usually go much past my belly button. A good rule of thumb is that the baby should ride somewhere between your breasts (or chest, if you're a man!) and belly button. When you wear the baby in this (and any other) one-shoulder tie, make sure the sling "caps" your shoulder and upper arm and doesn't ride up towards your neck---that will get uncomfortable really fast!
There are LOTS of ways to carry a baby in this tie. Here are some.
Cradle carry
The cradle carry is best for most little babies, since they are fully reclined. It is also the best way to breastfeed, and can also be used for breastfeeding toddlers (I know this for a fact!), though you may find you need more room in the sling for breastfeeding (this is where an adjustable knot comes in handy---just loosen it a bit, slide the knot down, and tighten it back up---ta da!). You can position the baby's head towards the knot or away from the knot, but will find that in either case it is best if the baby is on a diagonal to the sling fabric, with her head towards the outer rail and her feet towards the inner rail. This will keep her from being "all scrunched up" and will also allow her to see the world around her (since the fabric isn't over her face).

To
get the baby in, hold her up on your shoulder and slide her butt down
onto the sling. Spread the pouch open around her, tucking her feet
inside, and lay her down into it. Make sure the inner rail is pulled
up between you and the baby. Many thanks to Saan for lending us her
favorite doll Anna for this demonstration!

The
baby can lie with her head on the opposite side from the knot...

...Or
with her head on the same side as the knot. And more thanks to Saan
for lending us her lion for these last two pictures, since she is now
too big herself to demonstrate the cradle carry.
T2T (tummy to tummy)
A lot of little babies don't like being held in a reclined position, however, so you may find the t2t position to be more comfortable. You will probably find that you need a tighter pouch for t2t carries than for cradle carries. For a little baby, it is probably better to tuck her feet inside the pouch either folded under or in front of her, but a larger baby or toddler's legs can be left outside the pouch. To get the baby in, hold her up on your shoulder and lower her butt down onto the sling. Spread the pouch up under her. The inner rail should go either completely over her legs and up between the two of you or well up under her knees so it is supporting her entire butt and thighs. Pull the outer rail up over her back. For a little baby, you may want to pull it up over her head to keep her head steady. Older babies and toddlers will probably want their arms out.

We
often use the t2t carry with Saan. Sometimes we tuck Anna in with her
as well, which makes life easier on me---Anna can come with us
everywhere we go, and I don't have to worry about whether and where
she's been dropped.
Hip carry

A
variation on t2t that's most suitable for older babies and toddlers (3
or 4 months +, I'd think)---simply carry the baby on your hip instead
of your front. This puts more of the weight of the baby on your hip
(rather than your shoulder) and gives the baby a more exciting
view---she can see what's coming and going, and can always take a
break from the action by resting her head on you.
Buddha carry
This is a good way to give a little baby a good view of the world. You may find that this position puts a little more stress on your back since the baby's center of gravity is farther from you. You will also find that older babies and toddlers are too large to be held in this position.

Here
is Anna demonstrating the buddha carry for me.
To put your baby in a buddha carry, hold her in front of you, facing away from you. Lower the baby into the pouch, crossing her legs in front of her. Make sure that the inner rail is pulled up between you and the baby and that the outer rail is pulled up well in front of her. You may find that you prefer the outer rail tighter for this carry or that you prefer the middle (non-rail) part of the pouch to be larger. If so, just keep that in mind when you tie the knot and adjust your tying appropriately.
Adjustable rail tie
Some people prefer not to fold the sling before tying it---they feel that this gives them more individual control over the tightness of each rail and of the middle of the sling. Perhaps it also stays capped on your shoulder (not sliding up towards your neck) better? This is tied and worn just like the pouch tie, but the full width of the fabric is spread over your shoulder and across your back, and you have to spend a little more effort finding the appropriate tightness for the rails.
Knot in back
Still others not only do not fold the sling before tying it, but prefer to wear the knot on their back (usually just behind their shoulder) and sometimes flip the shoulder of the sling over, which has the effect of tightening the inner and outer rails. This is nice for making a headrest for a cradle-carried baby, but I generally find this carry less comfortable since not only is the baby's weight spread less uniformly over my back, but there's a big knot back there!
Cradle cross

Instead of tying the sling at (or behind!) your shoulder, you can put
it on by draping it (folded or not---take your pick (if folded, keep
the fold towards the outer edge of your shoulder) over your shoulder and
bringing the front and back tails towards the opposite hip.

Cross
them with the back tail over the front one. Bring them back
around to the other hip and tie. This is a nice way to distribute some
of the weight of the baby to your hips, but I find it more difficult
to get the inner- and outer-rail tension adjusted correctly.

Here is
Anna held in the cradle cross position.
Hip cross
The same tie can be used for a toddler hip carry, and I find this to be the most comfortable way to wear the rebozo. It's possible to tie it without the baby in it (as shown above), but when I do that I find it's very hard to get it comfortable. I find it easy and super, super comfortable to tie it on around Saan. This carry is very "poppable" and is GREAT for nursing---I just loosen the knot a bit and let out some slack to lower Saan down a few inches and pull the fabric high up her back---totally hands-free nursing! Yahoo!

Begin as with the cradle cross carry, with the rebozo draped over one
shoulder. I prefer to leave more "tail" in the front---this allows me
to tie the knot in the front rather than trying to reach around and
tie it in the back or on my side.

Pick
up the baby and hold her on your hip where you'll want her to rest
when the tie is finished. Wrap the back tail of the rebozo behind your
back and then across the baby's back.

Wrap
the tail tightly around her, spread well across her back and under her
butt, and tuck it under her leg. Believe it or not, the pressure of
her leg will hold it there while you finish the rest of the tying.

Now
pull the front tail of the rebozo tightly across you and over the
baby's back (spread well across her back and under her butt) and tuck
it under her other leg.

You may want to spread the fabric "crosses" more across the baby's back.

I
really find this super-comfy and can wear it for several hours. (Saan
seems to like it, too!) Allowing the fabric to drape down my arm seems
to spread the weight better, but when I need to use my arm more, I
either tie it so that the fabric rests mostly on top of my shoulder or
just scoot the fabric up there for a moment while I'm reaching for
something (and then spread it back down).
Alternatively, you could put her inside the entire "X". This is not quite as secure underneath (since there isn't fabric going under her legs), but I find it stays up higher on the baby's back when she's into "arching", and thus supports her a little better.

Drape the sling in front of
you, with one tail going back over each shoulder.
Place the baby into the pouch made by the fabric in front of you and tighten the inner and outer rails using the tails.

Either cross the tails behind you or bring them directly back under
your armpits.

Then
bring the tails in front of you and tie under baby's bottom. Tuck a
young baby's legs in either under or in front of her and bring the
inner rail up a bit between the two of you. Leave an older baby's legs
out but make sure that the fabric is pulled up well over her bottom
and up to the backs of her knees. If you have enough fabric left over,
many people find it more comfortable, instead of tying the sling under
the baby's butt, to simply cross the ends under her butt and bring
them behind your back to tie, since this helps distribute the weight
to your hips.
The simplest way to get an older baby on your back is simply to hold the baby on your hip and slide her around under your armpit to your back. This is a little tricky with a floppy little baby though. Another relatively easy method is to spread the sling out on a bed or chair and lay the baby inside it. Then lean back over the baby, grab hold of each end of the sling and pull tightly to hold the baby to your back as you lean forward to do the tying. This method can be modified for an older baby by draping the sling over a chair and sitting the baby up in it. If you're feeling adventuresome, a really quite easy and secure (but scary sounding) way of doing it is to place your baby in the sling and hold the two ends quite tightly so your baby is completely bundled within the sling and then swing her gently onto your back.
Here are some pictures of me using the latter method to get Saan up on my back.

Wrap the rebozo around the baby, covering her from shoulders to knees (if it's a little baby, cover her head, too).

Hold
the rebozo with two hands. This looks strange, but is really very
secure. Saan thinks it's hilarious.

Gently
swing the baby around onto your back, keeping the tails of the rebozo
in front of you.

Bring
the left tail (in the case of this picture) over your head to the
other side of your body. Hold the tails taut; this keeps your baby
pressed safely to your back.

With the baby on
your back, drape the fabric over both of you. Make sure the top of the
fabric comes all the way up your baby's back and that the bottom
completely covers her butt and comes all the way out to the backs of
her knees. Bring both ends of the fabric over your shoulders.

Tighten both the inner and outer rails well and either bring the tails
right back under your armpits or cross them in front of you before
bringing them back under the baby's bottom.

If
you're skinny enough, you can cross them behind the baby and tie them
in front of you. I am not this skinny, so i tie under Saan's bottom.
By tying the sling tighter, it is possible to get quite a high back
carry with the rucksack tie, giving your baby a wonderful
over-the-shoulder view of the world around her.

With your baby high on your back, wad the sling up lengthwise and
bring it behind her back and under each armpit.

Now bring each end over your shoulder and either cross them (I find
this a little choking, but some people like it) or bring them straight
back under your armpits and tie under baby's butt (or, if you'd like
(and are skinny enough!), cross the ends under baby's butt and tie in
front.
The secret of this tie is to have the baby high on your back and to tie the sling TIGHTLY. This way the baby isn't suspended from her armpits but is held to you by the tension in the sling pressing her to your back. Try giving a little hop while pulling on the tails. Trust me, you won't squish the baby! If you're worried about a particularly active baby slipping her arms under the straps (and thus working her way out of the carry), you can wrap the sling around her front and cross it behind her back and then proceed with the rest of the tie as usual.
Traditionally, Korean women did this carry without using the shoulders at all. After they passed the sling under their arms, they simply crossed it over their breasts and brought it back under their arms to tie under the baby's bottom. Lots of people swear by torso carries like this, but they've never seemed particularly comfortable to me. Perhaps they're best for very busty women??

For more ways to wear your baby, check out Mamatoto and The Babywearer. For more information on rebozos and their use in childbirth and traditional societies, check out the Rebozo Way Project. For more information on this particular rebozo, check out Ellaroo (the rebozo shown on this page is a rebozo-length wraparound in the fabric Ysabel).
Happy baby wearing!