1) The vast majority of people at university are not as intelligent as you might think they should be before you start. The ratio of intellectuals to absolute dunderheids isn't too different from what you get in a standard high school.
2) Don't go anywhere near the union, the library, or other communal student places during student elections. They are completely and utterly pointless and you will just be harrassed by 20 consecutive morons in the space of 10 yards.
3) Facebook is pointless. Don't even bother with it.
4) Textbooks are pointless, don't buy them, don't even think about buying them. If you truly ever need one, it'll either be available for download on a dodgy website, or available in the library. But the chances are that you won't need them... ever.
5) Most lecturers are terrible at lecturing, and you're better off staying in bed, getting the notes off mates and self-teaching. That's the case for me anyway and I soon learned this trick after a few semesters... attendance in the final 2 years was close to 10%, but still pulled off a first with ease.
6) Never trust a lecturer's "exam hints". Even if they flat out tell you that x will be in the exam (or, more annoyingly, that it won't be in the exam), don't trust it in the slightest. Treat all exam hints like you never heard them, learn the whole course, otherwise you're spelling disaster for yourself. And contrary to popular belief, if a lecturer says something won't be in the exam, and then it is, you actually can't blame them for your failure. If it's in the syllabus, it CAN come up, so learn it.
7) People who act cocky in uni and seem to be on top of all things at all times are usually the least capable people, usually on top of nothing at all times. Even immediately after an exam they will give a fist pump and sport a great big cheeser. Come exam results day, everything is different, and you find that the people who were most critical of themselves, least confident and unboastful get the best results.
8) Don't compare answers with people after exams or even before handing in courseworks. ESPECIALLY not the people I talked about in 7). They'll tell you you're wrong, and you'll doubt yourself, and possibly even change your work to be more in line with everybody else's results. Come results day, you'll regret it. Not only will you be in trouble for plagiarism, but you'll have been wrong when you were originally correct. I don't know how many times I was the only person who got a particular question right and the rest all had the same wrong answer. Democracy doesn't work in academia.
9) Graduation is nothing but a pointless excuse to rob you of ridiculous sums of money for terrible traditions. Don't go. Get your degree in the mail, save yourself several hundred pounds and celebrate at a venue of your choosing.
10) Once you get to uni, your parents will cease to be amazed by your actual work, as they'll have no clue what you're on about or what you do. They'll be proud that you're "at uni", but you might as well be doing Underwater Basket Weaving for all they care.