Once your baby is born and you first arrive home, let a friend or family member take the baby for a few minutes so you can go into a room with just your cat to say hello. Once you've become reacquainted and he is comfortable, allow others into the room, including the baby. He may take off to avoid the chaos and that's ok, don't force him into meeting the baby as this could create a negative relationship. Instead, give him a used receiving blanket or article of baby clothing to sniff and investigate at his leisure.
When putting the baby down for a nap, it's best to leave the door of that room closed so the cat doesn't jump into the crib and take a nap too. This is a huge smothering hazard. Consider installing a screen door instead of a regular door so the cat can see what's going on, and doesn't feel completely shut out. If there is no door, you can purchase crib netting to keep the cat from jumping in.
It's important to remember that the baby was brought into the cat's home, and the cat was your baby first. As hectic as life with a new baby is, the cat will still need and expect your affection every day. Use the baby's nap time to have some one-on-one time with your cat so he doesn't feel neglected.
A few other reminders for encouraging a positive relationship between your baby and your cat:
Keep the cat's food and water out of baby's reach
Regularly use flea & worm treatments on the cat, and make sure they are safe to use around babies
Never leave your baby and cat alone together