Shadows, Wrinkles, and their placement....?

So i'm trying to focus on lines, shadows, and wrinkles in clothing right now....I never understand where to put them, how they should look, so i'm stuck copying someone elses so I can maybe learn to understand more. And trust me, I am starting to understand way more things.  Like light, and highlights, and coloring.  But theres still a lot more to learn.  I'm going put up some youtube videos about wrinkles, lines, and shadows here in a minute, so you can learn with me! 

LOL!!