Done from photo reference for a sweet independent study class that I'm lucky to be taking.
What's wrong with my muscle placement?
How about her right arm, too short?
Does her left toe look like an uncircumcised penis?
Anything else look like a honkey-tonk-wonker-doodle?
There are a lot of things wrong with the muscles and their placement. One technical critique is that you're missing the two hip flexor muscles, I don't remember their names but that center quad muscle is supposed to stick out between the two of them. Another one is that the pec and delt are joined into one muscle.
Compositionally keep it simple and just stick the figure in the middle of the picture, make it easy for people to look at the image. I think for now it would be best to stick with line work. Get some photos, or drawings of figures, and trace their silhoettes, concentrate on proportion.
"Beliefs are rules for action"
"Knowledge is proven in action."
"It's use is it's meaning."
Worry about the proportions before all the muscle definition - this character is all over the place.
Definitely second MiniGoth's comment- the proportions in a figure are far, far more important than the anatomy at first. You can get all the lines and curves from proper anatomy down to a science, but the first thing someone is going to see is "that arm is too short" or "that thigh is too thick". Worry about the big picture first. Loomis and Bridgman are great resources for this.