buying used camry

We're in the market for a used 1999-2002 Camry. We'd appreciate any used car buying tips such as negotiating a fair price,checking out vehicle history,etc. What kind of discount can we expect from dealer retail price? We will have no trade in and will pay cash.

Any publications or websites that could help guide us would be great. We live in Iowa and would anitcipate buying a Camry from a State that uses little or no salt on it's roads. Iowa's not bad,but used cars in the upper midwest rust badly.
Thanks,
P Sully