I used to get quite a bit of clicking in my shoulders, especially my left one. It was mainly caused by overdoing bench press without also matching it with and equal amount of rows/pullups. I now do equal amounts of press, OH press, rows and pullups and my shoulders are fine. Doing shoulder dislocations with a broom helps mobility too but my god does it hurt.
Also, to the guy with APT - I have that too. It's a combination of something I've had since I was very little, and a lifetime of desk jobs and poor posture. Ab strengthening/hip flexor stretching is definitely the way to go but I've also had good results from deadlifts surprisingly enough. Strengthening your back seems a bit counter intuitive but the glute/hamstring strength I've developed has definitely helped with my posture. Having good back muscles has helped my hypermobile spine too.
I do straight back-stiff leg deadlifts (
link) with lightish weights (50-60kg) to work my hams, and more regular, heavy (110-120kg) deadlifts from the floor to work my glutes/back more.
I do my regular deadlifts with straighter legs than usual though, because I'm nursing a quad sprain/impinged fat pad in my knee, and because getting a good hamstring tension before I lift emphasizes my glute involvement.
I really don't do as much ab/hip flexor work as I should though...