Leg padding for which pouch?
Shoulder padding for which pouch?
There are 2 fundamental principles to safe and enjoyable babywearing: 
TENSION and ATTENTION.  It's really quite simple. When you put a baby in a sling that you are wearing, the weight of the baby's body puts the fabric under tension. This tension holds the baby in place so that when you move, the baby and sling will move with you as a unit.  The baby is quite securely attached to you.  However,  it takes some attention to safely sling a baby.
Things to think about & answers to FAQ's
Those of us who sling our babies take full advantage of that fleeting time in which  babies & toddlers want to be held.  It's a very small window of opportunity.  If you practice babywearing, you are making the most of that opportunity.

*Every time you put a baby in a sling, inspect the seams and fabric first. Don't forget! All things, even slings sewn with the level of care that goes into my slings, wear out over time.

*Look in a mirror and note how your sling rests on your body.  The sling should slightly cup your shoulder and the seat of it shouldn't fall below your hip bone.  The sling should also feel almost "too small" or tightish.

*If you are new to babywearing, practice first with a toy or doll in front of a mirror. Or, practice with a willing cat or small doggy.   (You'd be surprised how many pets love this.)  You can also use a bag of rice.  When you try out a new position with a baby in a sling, watch closely to make sure your baby is ready for the new position and is securely seated in the sling.  There should be sufficient tension in the sling to keep the infant in place. 

*A baby in a sling should always have it's head higher than it's bottom.  Always.

*Support young infants' necks and heads as you position them and watch closely when they are in the sling to make sure their spines are properly supported and that the baby's chin isn't closing off his or her airway.

*Many young babies like to snuggle so tight in the sling  that you wonder how on earth they can be comfortable.  And yet, they are.  Conversely, many toddlers and the exceptionally curious will sometimes lunge quite far out of the sling to reach something.  You wonder how on earth they manage to stay in the sling at all.  And yet they do.  Many babies seem to have a pretty good instinctive sense regarding what they can or cannot do safely within the boundaries of a sling.  If a small baby fusses and fusses in a sling, it's usually because they aren't positioned quite right.
 
*Don't be discouraged if a baby doesn't seem to enjoy the first few trips in a sling or if you at first find the sling uncomfortable. Like everything else in the world, babywearing takes some degree of fidgetting and settling in to get it just the way you like it.

*If you bend over with a child in a sling, hold the sling close to your body with your free hand. If the sling fits properly, babies should not fall out on their own. However, you never know when a baby might make a grab for something on the floor while you are bent over.

*Any sling that is too long will pull at your back uncomfortably.  With pouches, you can often give the fabric a twist just below the shoulder area to cinch it up a bit.  With a ring sling, get to know those rings!

*Never leave a sling out where children or babies can get tangled in it (such as putting a sling in a crib with an infant.)

*Use common sense when you have a baby in your sling. It is easy to be too casual. Beware: If you prepare food, light matches, smoke cigarettes, drive vehicles or eat hot food and liquids while wearing your baby in a sling, you may jeopardize your baby's safety.  It's best to err on the side of caution.  If you ever question a babywearing action's appropriateness, even just an inkling of a qualm, then don't do it.  Be safe and be responsible for your actions. 

How to Thread a Ring Sling:
  Tips and truely useful tidbits to get the most out of babywearing.......
Using a receiving blanket to pad slings for wee little babies and babies with low muscle tone:
This can also be done with a kitchen towel, clean prefold diaper, etc.
You want the pad to be just a bit wider than the baby's body and to rest directly under the baby's upper back  and head.  If you place the padding in the sling before you put the baby in, the padding helps to hold the pocket of the sling open.
How to Reverse the Tail of a Ring Sling
To see a timeline of babywearing positions......