Check the painwork for overspray, generally a sign of the car having an accident before.

Best to have the seller start the car for u when it's cold, check to see if the engine vibrates alot when it starts and also for abnormal noises. Check for leaks on the engine block, reference the last service date and check the engine oil to see if it is consistant. check handbrake, use all the 6 gears in the car (including reverse) check the idle of the car during warming up and after.

Car steering abit to the left is normal, check the brakes, see if it shudders or screech.

Bounce each end of the car to test the suspension and shocks, it should stop after one bounce, if it doesn't, it's stuffed..

All these basics plus a few other bits...

My advice is if you are not sure what to look out for, get someone who is versed in mechanics to follow you...