each sport works differently.. some i know have weekly comps like the union, league,afl, netball and bball teams but others- waterpolo, golf etc only compete at uni games. selections are run by the sports council which is a group of students who are elected to the positions. other sports include dorm sports- a weekly campus competition i in which dorms compete against each other as well as other student teams in tough football, cricket, european handball, netball/basketball and soccer... i hope that gives you a bit more insight!