buy a used car from someone you know...that way you'll be somewhat familiar with it, and if they value your friendship, they won't rip you off too badly.....

I've had good luck (with emphasis on the word luck) with buying a van off ebay. Trick here is ask lots of questions...get a vibe from the seller. Call him/her on the phone and talk talk talk. I got a van for about $2400 whose bluebook value, according to my county clerk's office, was about $7100....the county clerk didn't like that too much and made me jump through all kinds of hoops to title it in my state, because they were losing a fair amount of sales tax they could charge me (bastards, screw them)....I got the van so cheap because the guy was moving across the country and needed cold hard cash (and I was the highest bidder, of course). I drove it back 600 miles no problem. I have driven it lots since I got it home and knock wood I haven't found anything wrong with it yet.

Sometimes you can do well at auctions also. You sort of have to know what to look for though. The ones I've been to, they don't let you drive the vehicle, but if the key is in it you can start it up, put it in gear, move forward and back a few feet, etc.

Check the oil and coolant before starting up. If the oil has white filmy stuff in it, coolant is leaking into the oil galleries, and that's not a good thing. It means the motor needs major work. Check to see if the oil looks clean. Of course, the seller could've just changed it before he put it in the auction, but if it's dirty (black) it implies some negative things about the seller, like he probably doesn't take very good care of his vehicles. Look underneath and look on the ground to see if anything is leaking out.

Check coolant and see if it looks clean (lime green). If it's rusty looking, it's dirty and hasn't been changed in a while. That can mean the coolant system is corroded as well.

Turn the key to "On" without starting. Check if the idiot lights all come on (oil, battery, check engine, temp, etc). If not, it could mean that some of them were disconnected to conceal a problem.

Start car and check the exhaust for blue smoke. If so, that means car is burning oil, not good. Hold brake and put car in gear, check to see if transmission shifts smoothly or "clunks" into gear. If it clunks, drive train could need work in the neighborhood of a few hundred dollars.

Once car is running you can check to see if A/C, heater, radio, etc works.

Auctions I've been to, once you've won the bid on a car, you have about one hour to drive it around, check everything out, and if you find something majorly wrong, you can bring it to the attention of the auction manager to seek some sort of "redress of grievances." I've never had to do this so I can't comment positively or negatively on this (sometimes the engine and drivetrain will have some kind of limited warranty - 30 days perhaps - that will be included as part of the sale).

My ex bought a SUV this way. She got it for about $2k less than what it "booked" for. We drove it and I noticed a "bumping" noise. I'm thinking the rear end/axle is bad, and I go back to the auction manager and tell him about it. He drives it and says it's a defective tire, sorry...no refund or rebate or anything. Oh well, I can live with that. That was about 5 years ago. She's still driving it. (new tires fixed the problem)......

This is just a smattering of things to check for. Hope it helps. Best of luck to you.