This is something that I have trouble with and am working on so heres something that I think about when I draw wrinkles, Im terrible and explaining things verbally but I hope the visual aid will help some while this helps others??
Well anyway, try to think of this in terms of isosceles triangles. The two equal legs of the triangle are the direction in which you draw your wrinkles. This is to break up the composition, and to force you to recognize the multiple directions the weight in cloth falls in. The other leg represents where the slack in clothing would start, for instance, (on a soft shirt) are there wrinkled right on your shoulders? Or when you wear a skirt, are there wrinkles on yo buttcheeks? Nope, because something is straightening the cloth there, wrinkles are under those places.
You should place the triangle around the area you think is causing the wrinkles, like your bodacious booty. Wrinkles crease to the pull. Also think about looking at some actual wrinkles. Actually definitely do that. Looking at the real thing will allow you to develop your style first. After you look and think about your approach you can look at drawings and stuff, because that helps you with the actual execution.
I guess thats all? If you have any questions or want more information please stop by my ask! Im pretty bad at explaining but I can try to give you some of my perspective, because what works for some doesn’t work for all!