My sister and her husband lined the crib with tin foil to train the cats not to jump into it before the baby was born, I think that was the only real preparation they did.
This is a great idea. Wish I'd known about this when I was pregnant with my oldest. We had two cats when our oldest was born, and the only sticking point was that they really, really liked the Moses basket where our daughter slept for her first six weeks. We simply shut the door to the nursery to keep the cats out. Apart from that everything went fine.