Talk to the child about the baby from your child's perspective: "you are going to be a big brother", "she is your baby sister", "this is our baby".
Look at baby pictures of your older child so that she can understand she was once a baby too.
Read him books that help prepare him. Some of my favorites (and my son's) are:
Mommy's Lap by Ruth Horowitz
Cornelius P. Mud, Are you Ready for Baby? by Barney Saltzberg
I'm a Big Brother by Joanna Cole
Talk about ways that the older child can help care for the
baby. She will be happy to have an important role in the family.
Encourage your child to participate in activities to prepare for the baby, such as putting the baby clothes away or decorating the baby's room.
Avoid any additional major changes right before or after the baby is born.
Plan for your older child to stay with someone who she is familiar
with while you are in the hospital.
Please share your experiences and tips of helping your older child prepare for the new baby.