To add more folds and wrinkles I like to use CUT with 3 or 4 divisions..
Moving the points around you can make sharper or smoother triangle shapes. CUT will follow the direction of your selection making it possible to quickly change the direction of a new fold..
For overlap and clustering of folds follow the same procedure but try to move small groups of points above each other.
I hope this will get you started but remember that this is not set in stone, by all means experiment and see what works best for you. Happy folding!