Advice on buying used cars

I’ll need to buy a car pretty soon, most likely a used car, but I’ve never done it before and I really don’t know too much about how it works and what I need to look for.

Which cars are good to buy used? I’m mainly looking for reliability, especially in the long run. What should I ask the salesperson when I’m at the dealership, and what should I look for in the car (like mileage etc.) and during the test drive?

Also, to get a loan, do you need a good and extensive credit history? Or should anyone be able to get it?

Are there websites that can give me more information?

Thanks.

Jam it back in, in the dark.