Look for relative movement between parts and work down the chain. eg: Grab the wheel/hub with one hand and knuckle in the other and push and pull them violently in opposite directions as if you're trying to pry them apart, then do the same with knuckle and tie rod, then tie rod and rack body, etc. When you find a clacking sound, you've found your problem. Feel for the source as well is listen.
If the play is *only* left to right and definately not up and down, your problem lies in toe control which is all steering system. You can eliminate strut, wheel bearing, and ball joint.