You could do a search on this topic because its commonly discussed, but in summary:
Men:
belted trousers with long sleeve collared shirt; tie and jacket usually optional unless told it is more formal
no sneakers, jeans, shorts, sweats, etc. unless otherwise told the event will be held in a gym
Women:
at or below knee skirt or trousers with blouse or flat knit sweater
no jeans, sneakers, shorts, sweats, midriff or arse crack bearing clothing unless otherwise told the event will be held in a nightclub and you are the entertainment
Remember, you are being evaluated during these events, so don't look like a slob. Some do come in suits and that's fine but almost always these are pretty casual events, so "business casual" is fine. Check with the program coordinator if you have any doubts.