Speaking of clothing folds, how do you even do that?
I've been starting to draw more often now that I have an intuos but I honest to goodness can not draw clothing folds or anything like that.
The best way to learn is observe, obviously. different fabrics fold different ways and demonstrating smooth folds vs jagged folds will make your clothes all the more believable.
But a picture that really helped me out, and made it all "click" for me was this:

from
this blog post. I'm sure there are much better tutorials out there, and it would be best to look for them as well, but this picture demonstrates the basics pretty well, i think. The most important thing about folds is tension (or the lack thereof) and imagining in your head how that stretching affects the fabric. But of course, it's not easy to just "imagine" it all so that's why i reccommended observing from life too :p