You mention about other extra curricular/non animal stuff...
Basically vet schools want well rounded people, so good academic record, good work exp and other stuff as well. Make sure you put enough effort into school/college that you will tick the boxes on that front. With regards to other things, there is no point *just* doing something for your uni applicaton, but do things that you would enjoy anyway. Duke of Edinburgh award is always a good one (and can be started at 14), scouts/guides/cadets, non animal voluntary work, music/instruments/acting, playing sport for teams etc etc. All stuff which may seem very non-vetty, but develops important skills - teamwork, leadership, confidence, organisation etc.