First be sure your wheel bearings are tightened to specs...
otherwise they can make finding looseness in other things hard....
When they are tight if you go under the car with the engine running and someone slightly moving the steering wheel back and forth you can put your hand at the point where two items come together and feel movement in one compared to the other one....
So your hand would typically be spanning a ball joint type socket... you can feel movement/(lack of ) much finer than you can see it....
I would start at the wheels and go in feeling for play....