In this video, Ellen demonstrates threading a ring sling and then doing a hip carry with a baby. Ann Marie also demonstrates nursing in a ring sling. One thing Ellen never specifically mentions, but DOES during the video is that when adjusting the sling with a baby in it she lifts the baby's weight off of the sling before tightening. This keeps the fabric from twisting in the rings. Another tip to remember is that when you finish, baby's bottom should be lower than his/her knees and his/her bottom should be about level or slightly above your belly button.
Finally, in the nursing portion, covering for modesty with the tail is mentioned. I STRONGLY recommend not covering baby's head with the tail, only cover your body. As you can see, even without using the tail, there is nothing showing when I'm nursing in the sling. You would be amazed at how often someone comes and sticks their whole head in to see the baby without realizing I'm nursing, and I never cover her head. Covering the baby's head makes it impossible for you to see if she is having breathing distress. The few moments between you "checking on" the baby under cover might mean the difference between a baby having a moment of distress and a baby smothering accidentally. I would never cover my baby's face out of a sling, I think the same should apply when baby is in the sling. Like all nursery products, it is important to monitor your baby at all times. Another note on nursing, most moms find a nursing top or a V-Neck t-shirt is easier to nurse in when using a carrier. I have to fish the whole top up through the carrier which isn't as convenient.