My daughter's first pediatrician had these helpful hints:
Put some of your expressed breast milk in a bottle. While your baby has the nipple in her mouth, dribble a little of the milk onto the nipple area so she gets a little taste of it. She should latch on. If she is not actively sucking, then continue to dribble the breast milk from the bottle.
Take a nipple and place it over your nipple. The baby should be able to attach to that nipple. Once she has started to get some milk, remove her, then remove the nipple and try to see if she will latch on.
Sit the baby with her legs hanging over your leg facing you. Take the baby by the base of the neck and put her mouth over your nipple. (*I know, it sounds weird but this was the way my daughter learned how to latch on and since I had her cesarean, it was easier on my stomach.) She should get the milk better because she is sitting up and gravity helps getting the milk to her tummy.
Hope those hints made sense.