1) Accomodation deposits to guarentee your room in halls- these can be as high as £550 (Birmingham) and frequently its not made clear that this needs to be paid before student finance comes in. Very few prospective students have £550 to spare and whilst some universities are sympathetic and will delay payment others seem to have a 'tough luck' attitude if you can't afford to pay.
2) When exams are. I started at UEA not knowing that they didn't have January exams until just before Christmas! Would have been nice to know earlier.
3) To add to whats already been said about modules, I don't understand why they can't publish module guides on their websites like the ones they give to current students, obviously I can't speak for all unis but at UEA all of them are already on the computer system for current students to see. Yes modules do change sometimes but not all at once so at least some would still be the same when the student started.
4) Inform and educate schools about required subjects and debunk myths that the university is too 'posh' for state school pupils, encourage schools to put pupils forward e.c.t then the schools can pass this onto kids. I think one of the biggest problems with university admisison is lack of correct advice by schools.