first i don't really know what the pose of this guy suppose to be so i just do what is the most possible thing i could make..
now here comes the real thing, hope you pay attention
on the bottom picture i made a cylinder of some sort, one is turn to the right and one is turn to the left and one is just neutral.
you can think of this as the basic guidelines for the clothing, if it's turn from the right then the clothing is turn as well. if i remember correctly in anatomy muscles is almost similar to this.(too bad i didn't study it)
now you should think: what part of the body is being turn? leg? body? arm and so on. and you can make some guidelines on where it should be placed.
note that i don't do this and don't make some lines before doing it.(it's too much work and i hate too much work)
so anyway you should take consideration where the tight parts as well and fold are actually affected by that as well.. how you think of how it was affected is up to you.
other folds are affected by tight parts, and other fold are affected by the movement. the best way to understand this is to look for real life, talk to your friends and ignore what their saying and just focus on what fold their clothes have.(just don't do it to girls or you might be mistaken as a pervert, hey wait! it's much worse if you get mistaken for a pervert from guys)
anyway hope this helps, i got this info from a drawing book, although it's not the drawing book i gave you.
i just like to add that folds differ from what type of clothing he/she wearing. leather, plastic yadda yadda. and ofcourse if the shirt is tack-in in what i did here, it's still different if it's not.
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