1) Cracks, easy deflection, wobbles are a good sign that the bushing isn't doing its job
2) Control arms and track bars, ie the constraining links
3) For any constraining link, a wobble, clunk, loose/vague steering feel
4) For control arms, I'd recommend moving away from bushings alltogether but it's not exactly cheap. Currie Johnny Joints are the best option. Otherwise, get some new or gently used stock replacement arms. I practically give them away. For track bars, Currie is the best option there as well. Otherwise, stock replacements will suffice.
Here's one recent testimonial, and that's only the lower arms: http://www.jeepforum.com/forum/f9/in...-lcas-1420526/
You'd be amazed at how much better the handling and drivability of your Jeep can be. It's probably terrible right now.