Make sure you got your passwords to your account. You can go now and get the "express checkout" approved for one of your credit cards so you need not go through the checkout process.
DO NOT be disspaointed if pre-orders do not start right on time. I have seen them start later. Just refresh your screen till it let you through.
I got the 5 and 5S via preorder early in the am and it only took one try for each and was quick. Hoping Apple will do even better this year.
Apple will be renting server time from Amazon, from what I hear, to take care of the millions fo orders.