I do a variety of stuff...but I've found when I use what I was taught in school I get better proportions XD But then I get in a hurry and I have to go back and fix stuff XD (I am by no means a great artists, in spite of school XD XD)
But I finally broke down and got a hand model so that I could improve on hands. I still use my own hands for some poses, but the model breaks down the joints so I have a better idea of what I should be doing (I don't...use shapes so much any more, but they can be helpful).
I also use references when I'm doing a full body and wanting to focus on proportions. I'll use a photo, and do that extending arm and comparing heads to other parts to try to make sure things go where they belong :3 You know what I'm talking about?
Uh...and I sometimes use royalty free/library of congress images of buildings as references for structures. Buuuuut that's just me, and I have a lot of improvements to make ^_^