All pretty good advice here. Some things I'd add.
1. Get hold of some 'how to study' book. Follow its advice. Hit the ground running and build up your work habits from day one. I was a crammer at uni - I'd sit up the night before with the textbook. This wasn't much help with courswork that required consistent effort throughout the term. Learn how to take notes from books and papers.
2. Don't bother with those other subjects - do Social Anthropology.
3. About drugs. Cannabis is proven to damage memory - not what you want as a student. There is persuasive evidence of a link between cannabis use and psychotic behaviour - and I don't mean in a good way. If you have any history of mental illness in the family, don't touch it with a bargepole. A psychotic episode is not something I would wish on my worst enemy. In general most people inside the drug bubble look like arseholes to those outside. (cue lots of people going 'mammy, mammy, the nasty anthropologist said our lifestyle wasn't perfect').
4. If you're in a shared house and your name is on the phone bill, electricity, you'll have to learn to be firm, even confrontational, to make sure you're not left holding the financial baby.
5. If you fancy someone tell them. Don't be afraid of rejection. But don't develop a crush on your lecturer or tutor. And if you're female especially DO NOT have an affair with a staff member. Whatever line of bullshit he may feed you, trust me it's bullshit. I've seen this more than once. Adds: And it's a good idea to find out what your uni's sexual harassment procedures are. Don't deal with it via a whispering campaign, as I once saw.
6. Take up a sport - even if you hate 'jocks'. I've recently taken up running and wish I'd done it years ago. 50% of your oxygen intake goes to your brain - it can only help
7. Join SWSS. Only joking! You don't have to be leftwing, but where politics are concerned, don't be like the kid I had in Dublin who said 'what's the point of doing anything, nothing ever changes'. A lad of 19 shouldn't be talking like that.
8. When introduced to people, shake their hand, and repeat their names. This will help you remember them later, and will assist you in making friends.