You think you can do morning classes because you did in high school? DON'T DO IT!
Try and schedule your day from 9-5 so you get use to functioning with a regular schedule.
Go to seminars, learn stuff to impress people with. Don't get cocky though.
There is literally no popularity or social hierarchy, so no cliques to deal with. Just find a group of friends and branch out from there.
If you're drinking: a) Pour your own drink! Cannot emphasize this enough! b) Have a cup of water between every drink, will cut down on hangovers c) Don't be a loud drunk. You'll get on everyone's nerves and get the police called, and no one likes that. d) Don't mix liquor with liquor, and for the love of any and all god(s) don't mix liquor with drugs and/or energy drinks! e) If your friend is in a bad place, get a proctor or call 911, don't think they can 'sleep if off', you want to be safe rather than sorry.
Do extra credit! Not every professor offers it, so take it when you can. Your GPA (and scholarships) will thank you!
University is for expanding your mind. Talk to friends about their majors, attend their events, talk to someone you met about their religion or culture, take an english class on Lord of the Rings. Learn things you wouldn't normally take in high school.
Love might come, it might not, don't worry about it and it won't be a problem. You're still very young.
Get used textbooks instead of new ones. Download textbooks online. Go splits on books with some classmates. Your profs will ask you to buy the newest version of the textbook. Unless you need the book for the practice questions inside, don't worry about buying an older version. You could save hundreds of dollars.
Join a uRec class. They offer free classes for UNB full time students - there's dancing and yoga and more! Take something you wouldn't normally. You might surprise yourself.
McConnell Hall's food loses it's lustre real quick. Keep food in your room in case you don't want to eat there! Meal Hall also has myKitchen, a full kitchen where you can make your own food like nachos, smoothies, stir-fries, and some other things! If what's being served isn't appealing to you, go to myKitchen!
During O-Week, your friendly HOC members will make sure to wake you up bright and early to get started on the day's events. Prepare yourself for it! Shower the night before or get up earlier if you don't like loud awakenings. ;)
Wear flip-flops or water shoes in the shower! There ARE people who do go without, however, you don't know where their feet have been! Flip flops in the shower keep your feet clean from any potential dirt or bacteria (despite how clean our showers are). It's also a good idea to have a shower caddy to carry your shower stuff in!
Have fun. But because you're spending a TONNE of money to be there, do your homework too! Ask second years for copies of past assignments to practice your work or even just ask them for help!