To check the steering, center the steering wheel at straight-ahead and have a friend rock the steering wheel gently back and forth while you watch EVERY joint in the steering system. You should also watch the steering gear input/output movement to see if there is slack in the gear but this MUST be done with the steering gear in the center of its travel and the steering wheel at 12:00. You should be able to spot any bad joints, loose bolts, worn idler, etc. this way. Ball joints are tougher but others have covered that. You can push/pull on the top of the tires to test the uppers but it isn't 100%.