make sure your car seat is reasonably light. heavy car seat & baby after giving birth is not a happy combination.
as other posters have said - make sure you have fitted the car seat at least 1/2 dozen times before you need to use it
the last thing you need is the car seat and baby in the car and you standing their with the instruction leaflet while it chucks it down with rain.
make sure whoever takes you to the hospital brings the right bag
rest as much as you can when the baby is asleep - you don't know when you might sleep again
put a coffee table or something by where you like to sit and feed. make sure this has the cordless phone, bottle of water, mobile, TV remote, baby wipes and a couple of muslin squares as well as a few snack things that you can reach for when your baby falls asleep on you and you are by yourself and the TV remote is 'just' out of reach
when your baby gets older, just buy lots of identical socks, then if you lose one it doesn't matter
ditto magic mittens or gloves. I always buy at least 2 pairs that are identical
stock the fridge and freezer with easy to cook foods even if it is just sliced bread in the freezer and plenty of butter or spread in the fridge and twins of beans in the cupboard
and lastly treat yourself to some nice bubble bath or smelly soap so that when you get to have a bath or shower you no longer smell of regurgitated milk etc