I think you need to get some serious reference imagery, how much are you planning the modelling?

Get as much picture reference as you can, try and get side front and top views, a three quater would help too.

Look at the main muscle groups and bone structures, try and think where the edge loop placement should be, draw them directly on your reference, or even print a copy out and plan on that, note down possible problem areas, and the best way to approach the model.