Try also ebay.com and autotrader.com - to get a idea of the prices.
please don't do ebay unless the car is within visiting distance. i do a lot of dealing on craigslist, there are scammers so you gotta watch out.
when you first go to check out a car have it sit idling for like 2-5 minutes and just watch everything run in the engine compartment, check and make sure no CEL lights come on, check out the tires if low tread life knock off some from the price, see if its been repainted sometime if its an older car, then give it a test drive check all the electricals like horn/wiper/stereo/blinkers. then once the test drive is done let it idle again and watch it, make sure no coolant leaks or anything or any different sounding noises from when it was first idling. and make sure it brakes in a straight line. all i can think of off the top of my head |0