What does a car dealer have to tell you about a car?

Question by ergo sum: What does a car dealer have to tell you about a car?
I'm a first time buyer searching for a used car. I'm told the dealer will generally not tell when not asked. What can I ask the dealer about the car that he/she is obliged to tell me? Do I have to research the VIN myself or do they provide a detailed history upon request?

Also, how do you know you are getting a good price on a used car? I know that new cars devalue immediately upon purchase, so how can I tell

Japanese Car Auctions