Look into subd modeling and topology best practices. Whats your intention for the finished piece? Animation, game, just for fun? That also dictates some things
Looking good! The top and back of the head is a little flat. I know you're probably going to be putting a helmet on him but it'll still be good practice.
It would help if you could post up your concept. If your concept is a huge landscape or a huge industrial complex the practical advice would be different.
thanks Shiniku :) . i will practice the foundationals of realistic anatomy. but i'm also trying to figure out some nice proportion for a cool video game character.
Because some softwares triangulate the meshes in different ways and can lead to this kind of problem. It's always a good practice to triangulate your mesh before exporting it.
I don't know, looks like the designer has a visible brake drum assembly housed inside the wheel. It might not be practical but its definitely intentional.