What do I check for in cars at an auto auction?

I'm looking to buy a car from an auction and I don't know too much about cars. Just some basic stuff. How do I tell if a car is good and worth bidding on or not?|||do the auctioners let u start the car?If not, don't go for it. it will end up paying too much for repairs. If yes, bring a mechanic, so that you won't get ripped off