Don't go in expecting to get laid.
Don't go in expecting EVERYONE to like you.
Don't pretend to be someone you're not. If you don't enjoy drugs, (heavy) drinking or smoking, don't partake to be "cool".
DO talk to your neighbours.
Don't be other people's slave - they can do their own laundry, no matter how hot they are!
Don't get TOO attached to the people you meet in the first week. Unless you all feel very connected, chances are you'll drift off within the next month or so.
DO have fun and study in equal measure.
DO be respectful of others beliefs.
Don't get drunk and get stupid stuff tattooed on your butt. Alcohol makes your blood thinner so you'll bleed more. Also, no respectful tattooist will work on a drunk person, so that leaves you with the guy who blagged his way to getting a certificate and "forgets" to sterilize his equipment.
DO ask your professors if you have questions and/or find a particular topic difficult. For one thing, ITS THEIR JOB.
Don't feel obliged to go out if you're bogged down with work. Certain subjects have a lot more extra reading or essays than others.
Don't make an ass of yourself at freshers. Everyone will remember and laugh at the guy who danced around campus naked singing Let it go, but not for the right reasons. Try not to be that guy.
Don't try and be the class clown. It wasn't funny in year 9, and it CERTAINLY won't be funny now.