I'm to the point where I know exactly where the problems are, but I'm not good enough to fix 'em. Yet. But this is the first time I've ever drawn cloth that looked even remotely like cloth. What clicked for me was when I read the tutorials at
http://www.polykarbon.com. This guy's work absolutely rocks, and he's got a ton of tutorials that show exactly how he does what he does. He should probably write a book. His description of folds in cloth was the only one that's ever made sense to me, and I finally 'got it' after reading his tutorial.