David, you are doing a great job...so I want you to know that first and foremost.

Below are some recommendations for improvement, please take only as positive reinforcement:
1- You should clean up those small tri's as quads. Yes eventaully you will need a tri(s), but try to limit those.
2- You are beginning to squish the quads here, you want to try and keep your quads somewhat the same size throughout the mesh as a whole, however, when detail is needed...go ahead and make your quads spaced tighter (closer together).
3- Example of an area (follow those lines/edges from the butt fold up to the hip area) where you have disparity of sized quads, this might show up in your renders (suggestion 2 and 3 relate to the same subject).
4- This might be a line where you keep tight spaced quads, a detail area, the butt fold...have close spaced polys follow this line.

Modeling is hard work, I hope you don't take offense to these suggestions...as they are just that, suggestions. Ultimately, modeling something and then rendering it will tell you what is working and what isn't.
From experience these are areas that I would see as concerns.

I hope this helps.
DarkEdge

Comitted to excellence through art.