Cloth Fold Sculpting from David Richardson on Vimeo.
2 Hours walkthrough on how I do folds.. Here is a link to a dummy if you feel like you need to practice it too.
https://dl.dropbox.com/u/44350607/DavidDummy.OBJ
or get a nice 3D scan from the 3Dscanstore.com
Also suggested book to read:
Drawing People: How to Portray the Clothed Figure by Barbara Bradley
Dynamic Wrinkles and Drapery by Burne Hogarth.
