Things that helped me a lot:
-Examine available light, even when you're not photographing; where does it come from, is it harsh or soft, what effect does it have on objects etc...
-Try to see 2D shapes instead of objects (kind of esoteric, I know)
-Be aware about how moving left, right, up or down changes the relation between objects.
-Use a fixed focal length prime for a while.
-Especially on subjects that don't move: THINK and move around before you take your photo.
-Read comments on other people's photos, they may apply to your photography too
-Examine composition in movies and high end TV series
On the wildlife topic: Sure, you don't have little control over your subject, but that doesn't mean you have no control over composition. It's mostly anticipation, predicting where your subject is going to be. And remember: luck=patience.