If I know I am going to be out in public and will need to nurse Gray, I try to wear layers- a tank or tee that has a low neck underneath another shirt or sweater so that I can lower the bottom shirt while the top shirt stays where it is and my belly isn't showing. You can do nursing tops or tanks, too, but I've just found this is the simplest (and cheapest!) way for me to go about things a bit more discreetly.
To nurse while wearing your child, I first have baby or toddler in the sling. For smaller babies, I find the pouch or ring sling most comfortable with baby in the cradle hold. Keeping the bottom layer tee pulled down, just lower the neckline and have baby latch on. This bottom tee will keep your tummy covered and then the top layer can be used to hide any extra skin showing if you wish. In the photo to the left you can see Gray has his arms out. Where my hand is where I might be exposed. You can leave your hand there to cover up a bit or if you can get them to keep their arms in, see photo at right where the pouch rail is lifted up.
Of course, you don't have to wear layers. It is a nice plus for those of us that do like to hide our skin a bit. It gets chilly, too! Also, make use of your sling as a cover-up, too. If you are using the ring sling, the tail can be brought up over top.
In the mei tai, wrap, pouch, and ring sling I find that the tummy to tummy and hip carries work best with toddlers. When Gray nurses, he's usually "sitting" in the sling and will rest to the side or nurse "straight on" facing me.
Be sure to hold on to baby in a way you would be nursing without the sling. Then adjust the sling so that it is secure and comfortable for both you & baby. And practice! In front of a mirror is how I've learned that I'm wearing my baby the right way and nursing, too!
If you're uncomfortable trying this around others, I often will casually turn away or go in an area that is easy to get baby latched on. Once I feel "all together" I just go about as usual- and most likely no one will even know there is a baby nursing in that sling!
And I just had to include "my eye's view" of the sweetest little thing...
Please share any tips you have in the comments below.