If you are finding your sling uncomfortable or tiring, it's worth checking that you have it fitted as well as it can be. Having an experienced sling user to help you in person is ideal. As a second best, below you will find some tips that might help. All tips are relevant for slings. Tips marked * are also relevant for pouches.
Ring position Most people find it comfortable to wear the rings quite high, on or just below the collarbone. (If you like them lower, that's fine too, but keep in mind that the 'pouch' where the baby sits will be smaller.)
For the sling on the right, this is a comfortable ring position. With some slings, the rings can be worn even higher.
Shoulder 1 * The goal is to spread the weight evenly across the shoulder, whether you like the shoulder spread down onto your upper arm or not.
Shoulder 2 * If the shoulder is padded (or you like your unpadded shoulder unfanned), centre it on your shoulder rather than letting it crowd your neck. This is even more crucial for hip carries, where your baby's weight will tend to pull the sling against your neck.
Back * Spread the back of the sling as widely as possible. The more you spread it, the less strain you will feel. Spreading it as low as possible is the key - even a small amount can make a lot of difference to your comfort. If you pull your sling down at the back, in conjunction with moving it away from your neck, you should notice a definite improvement. This sling can be spread very wide!
Height of baby * Most people find they are most comfortable with the baby riding as high as possible.
For upright holds eg. Snuggle Hold, Hip Carry
Top rail * The top rail (top edge of the sling) needs to be snug to stop the baby from leaning back, which can be unsafe and is tiring for you. Tighten it by pulling on the top edge of the tail.
Baby's leg position * Once your baby is old enough to want her legs out of the sling, they should be wrapped around you (like straddling a horse), and not dangling down. It's safer, better for your baby's hip development, and more comfortable for you. Note. In the photo on the right, the edges of the shoulder have been folded to the centre to allow a bit more arm movement. This can be useful with a "fan" style shoulder.
Baby's leg angle * Baby's legs should be approximately parallel to the floor, with her bottom at the same level as (or lower than) the underside of her knees. This keeps her safely in the sling and reduces red marks. Pull the fabric (the bottom rail) down to her knees, make sure it isn't bunched up, and then tighten snugly. If there's lots of fabric, bunch it or tuck it behind her back, rather than under her legs.