Leave your room door open (obviously while you're in your flat!) for the first couple of weeks so you can meet other students in your flat
Go to the activity and fresher's fair and pick up loads of student free stuff - make sure you pick up the campus maps as well so you can work out how to get around
Insure your stuff - I knew someone who got there stuff nicked within an hour of arriving in student accommodation (they'd just popped out to pick up some food shopping!)
Get some of those passport-sized photos made before you register as you'll need them for your freshers uni card.
Sort out your student bank account before hand so you have some cash sat in your account (even if it is an overdraft) before you move in - you don't want to be a broke fresher in the first week
Check out our listing of things to take to uni - print out the list and tick them off as you pack them in the car before you go to university