From what I have seen, the whole car becomes like an "odometer" itself; when you see a car with virtually no wear on the inside and the car doesn't look like its been through hell, you know the kilometers must be close to what is shown, and there are others I have seen with nearly everything worn out with half of the expected kilometers showing...alarm bells should start going off. Best thing to look for are the small clues and things that just don't look right.