This thread has made me realise how much i'd love to be a fresher again! I don't think I just speak for myself when I say though, that the actual first week of freshers won't be the same as the rest of your time at uni (it should be loads better).
In your first week or two, you'll probably be feeling home sick, overwhelmed, SO tired, anxious etc..but it's still really important that you do all the things everyone suggested..going out, talking to anyone, doing things you wouldn't normally do..it's true that the friends you make in freshers aren't always the ones you'll stick with, but they make meeting new people easier in general.
Sounds cliche but alcohol really does help..the first morning, you're bound to have tons of funny stories about last night that you can share with your flatmates. Be pleasant to everyone and they'll be pleasant to you in return..don't be the person who gets in an argument in the first week!
For me, the months afterwards were the best, when I didn't feel home sick and was getting into the swing of things.
Try and get the work/going-out balance sorted after the first month or so...sitting in your room studying whilst your flatmates are out drinking is never fun, but neither are re-sits! When it comes to the important stuff, do it properly.
Just enjoy yourself, and good luck!