Could someone give me some advice? (Blender)

I’m modelling a character for a game based upon the concept sketch below:

How would I go about the cloth/straps wrapped around his torso/legs?

“Loop Cut and Slide”(CTRL+R) or “Knife”(CTRL+K). hard to get much of an idea from the concept sketch, but I would just use those two tools to do create the details. Use loop cut more loops, then adjust the verts. Though I suppose it depends on how detailed you want the mesh.