As for cracking...
I used to crack my knuckles all the time. Nowadays, I only crack my knuckles when I think that it has been a while since I've cracked my knuckles.
I really wish I could crack my back on my own. When I was working on
South Pacific at Arena Stage, it seemed that everyone in the cast knew how to crack backs. Some people did it standing up, others did lying down.
Hmmm... Anyhoo.... So, one day, I asked one of the guys to crack my back... WOW! Like bk, the sound was quite incredible, and I remember a bunch of heads turning in the back hallway when they heard the "pop-pop-pop-pop-pop" of my vertebrae. Needless to say, over the course of the next couple of weeks, I would ask Brad to crack my back again. And again. Sometimes, I would just stand in front of him, cross my arms across my chest, and wait...

I also learned a way to self-crack my back, but that's not as much fun.
