Well first of all, where do you live, and where were you looking for going in to vet school.
In the UK I think my friend says that there are only five vet school you should consider: Cardiff, Cambridge, London, Edinburgh, Glasgow and Bristol. These five schools are extremely hard to get into; my friend applied about two years ago.
You need to have a good knowledge in Biology but especially in Chemistry. If you are a UK student, you'll be expected to attain at least AAB at A-level, with some schools; Cambridge and Edinburgh wanting AAA. These A-levels should be in at least two traditional science subjects; but it is much more important to have at least one of these being chemistry. These requirements are quite similar to that of med school; which is still pretty darn competitive. When I went to med school I took, Biology, Chemistry, Physics, Psychology, German and General Studies. You obviously don't need to do five A-levels, but you have to admit, as they were all A's apart from general studies (which was a B) its quite impressive.
You need to show the institution that you are committed to their university and also to their course and for the development of your skills. Basically you need to be a jack of all trades, and a master in a few too. What I mean is, you need to be knowledgeable of something to a level. They like to see achievement outside of science. If you are sporty, do you have any sporting commitments and do you get awards. If you were like me, and practical, what kind of jobs did you have, where did you work, why and stuff. Maybe getting some work experience with a vet surgery; even as a receptionist, will count towards the points to getting in.
You should also be trying to stay on top of current scientific issues and have a knowledge of previous breakthroughs and important ones as well. In particularly focus of ethical issues; in your case vivisection especially. Know for example animal testing is a big thing, but not for cosmetics; only 1% of all testing. I dont know how old you are when you are thinking to go for it, but start reading so literature on science in particularly health and animals sciences. Stem cells, psychologies etc are a good thing to keep up with. Try the
NewScientist (but even more so their actual magazines. Also try reading
BBC Health News.
But just try to be enthusiastic but balanced. And dont be afraid to get your hands dirty xD