What should I do if my baby will not nurse?

Nursing. What have you tried and what has failed? Keep a running diary of what works and what doesn't. Ask friends and family what they have used and use the internet for tips and tricks. Only trial and error will allow you to figure what works for your child.
Ask for help. Don't give up too soon! You may benefit by consulting with a lactation specialist. You may be able to find one at the hospital where you delivered your baby. In addition, your pediatrician's office may also be able to help. Sometimes changing the baby's position while nursing can help or using an assistive device (such as a nipple shield) may be beneficial.