Again please excuse my rough drawings ;;; here is a quick and basic explanation!
While I believe everyone has their own methods to drawing creases and folds, here is one I usually follow. I don’t concentrate on details much but I focus on the general shapes of the folds- we all understand that cloth overlaps each other when it creases and such. My instructors had taught me its all about the triangles.
Whenever there is a tension in the cloth, it creates a focal point to that area that is causing the tension. All these creases basically form shapes like triangles! For example:
Holding up a cloth with two hands, all the tension areas are drawn to the hands holding up the cloth. See all the tension points creating triangular crease shapes?
Another example with shirts- if someone is wearing a tight shirt, the arm hole usually hugs around the arm pit more. (thats why you can tell if you are comfortable or not if you can move your arm around in a sleeve). With a baggy shirt, tension is created with the object holding the fabric up, and gravity is pulling down on the sleeves.
Its easy to get way too focused on the detailing of creases- let loose a bit! Don’t worry about making the perfect crease and fold or else you might end up a whole sleeve of unnecessary creases (unless if you are intentionally drawing a large baggy sleeve that makes a lot of creases).
Here are some photo examples~ this is one of Robert Downey Jr. because he is lovely to look at :>
ringsabel 