Which app are you modeling and rigging in? The general workflow usually goes as follows: * Model/Sculpt high poly (if there is one) * Model low poly (optimized geometry ready for a game) * Materials (UV's baking and shader work, usually in the engine) * Rigging (create the skeleton, controllers and constraints) * Skinning…
Yes, you generally want to combine meshes and clean them (reset transform & delete history) before you skin. If you end up needing to make changes to something afterward, like combining or splitting off meshes, you make copies and go through the process I outlined making sure they're "clean". In Maya you can generally edit…