Oktoberfest in munich this fall- help!?

ok, my friends and i are planning to go to oktoberfest this fall in munich. we've got a few questions about how this all works. do we need to have reservations to get into all tents, or just to get seats in tents? if we haven't made reservations, are we going to be able to get anywhere to get beer or food, or to reach dance floors? any advice you have regarding the festival in any way will be helpful. we'd also really appreciate any recommendations you might have for food or entertainment tents. thanks!