MOST IMPORTANTLY, ACHIEVE THE GRADES. SO........
Don't miss lessons e.g. attending too many open days can damage you chances of sucess if you miss lessons.
Instead: - use CD Roms to make a virtual tour of a university from the comfort of your computer.
You can then narrow the selection of Institutions you will actually visit.
 
PERSUADE THE ADMISSIONS TUTOR YOU REALLY WANT TO STUDY A PARTICULAR COURSE
Lots of students apply with suitable predicted grades so why offer a place to you?
Admissions tutuors must be confident that you will not drop out once you have started (they lose money if you do) so make sure you are convincing with your reasons for wanting to study that particular course. Evidence of additional activities/experience is vital. Subject specific open days, summer school residentials, subject conferences, related work experience or personal research will all help convince an admissions tutor of your interest in, and commitment to, a course.