Two of my own personal rules of character modelling are:
1. Finish fase 1 then 2 AND then 3.
Fase 1 is Basic mesh. very blocky but you create all the proportions such as: Body, legs, arms, head and hands size.
Fase 2 is Advanced mesh. Muscles, fingers, toes, nose, ears and so on.
Fase 3 is Finishing mesh. Finishing touches to every thing. Veins, nails, skin texture and so on.
2. Minimize amount of poly`s for better polyflow.
remove unneeded polygons. The less you use the better! use to much polygons and you notice that its harder to edit.
And some parts need lesser polygons then other parts for example: if i create a character i have way more polygons in the head and hands then in the legs and arms. More detail means more polygons.
Its just a few tips! i can see on your model that you use lots of polygons in parts that doesnt need that much.
its not easy but if i look back since the moment i use those two rules i see that my modelling is getting better then ever before.