I am now looking for an used car to buy and one thing that I was told was to ask for the license plate and ask in the brand stand if the miles/kilometers check, because some people can mess with that. Do you do this when looking for an used car?
No, I've never done that. Now, you can just get a Carfax and find out all of the little things that your vehicle has gone through. Not to mention, you can kind of figure that out in your head versus how old the car is. But, if you really feel like the odometer has been turned back, then simply don't buy the car from that party.
You can and should acquire an official DMV report on a vehicle rather than trusting CarFax, though. There are ways to get around CarFax, but a DMV record never lies. It's easy enough to change the odometer on a vehicle, even in vehicle with an electronic odometer. People get ripped off through this trick each and every day, although it's completely avoidable by being diligent.
Actually I called the Opel place where I used to take my car and they can check the kilometers the Opel cars have the last time they were there in service, so that was a huge help. I even took the car there and everything was fine, so it seems a good purchase.