These tips won't be the best ones, but it is what came into my mind:)
1: Check the body/paint work. Swipe your hand over doors, bonnet, fenders etc. and feel for uneven surfaces
2: Check the doors. After an accident, door might have been replaced, and it might have been not aligned properly
3: Try to see if the car is straight, from back to front or vice versa. You can spot uneven surfaces this way too
4: Check the pillars, roof etc. to see if it has any left over marks
5: If the car is a few years old, and the paint looks really fresh, snap your fingers at it. Hard metal will result in repaint
6: Take a test drive, you will feel it. Take hands off steering wheel, and accelerate a bit, if it turns left/right, might need Wheel alignment
7: At last, if you can arrange for a jeck, lift it up and inspect it properly.
Always bring a trusted mechanic/denter and an elder with you. It helps a lot.
Hope this was helpful, since i don't know much. My uncle's friend is a pro, and he does this for me:)
Good luck^_^
