Feedback and next steps on character model

Hello! I'm new to CGCookie, and I'm looking for some advice. Been trying to figure this modeling thing out on my own for a while, and I'm dying out here.

I'm trying to create a basic human mesh based on a character from a comic that I really like. But I've hit a bit of a wall, and I'd really appreciate some more experienced eyes to tell me what I can do better and what I should do next!

I've attached the blend file to this post, for closer reference.

The goal is to have a basic human mesh that I can then throw some clothes, hair, and textures on and ultimately have something at least resembling the target character that I can then rig and animate. I'm aiming to, just, go through the whole process from start to finish.

I have a lot of problems with where this currently is, and not a lot of ideas for how to fix them.

• I feel like the legs need more/better shape, but I'm not sure how to accomplish that. Adding more vertical loops to even out the lower body just seems to mostly jank up the upper body.
• I'm starting to suspect that I'm doing something terribly wrong in the groin area. The butt seems flat, and all that's between the legs is just two very stretched quads. I can see that I'm doing something wrong with the topology, but I don't know enough to see what I'm doing wrong? I would really appreciate some tips on how that whole zone is supposed to go.
• I have no idea how I'm supposed to shape the arms, the proper proportions and lengths of the forearm vs the upper arm, how to shape the elbow, etc. Would greatly appreciate some advice and/or references for how arms work.
• The body itself seems too thick, and possibly even too broad. The character is supposed to be pretty scrawny. How do you make a body scrawny?
• The neck and head are just roughly blocked in for now, but if anyone's got some pointers on how to do those right, I would be forever grateful.

All in all, I'd really appreciate any feedback on how  I can make this look better, how to fix the problems listed above, and what the next step would be in finishing this model.