The first thing I always do is gather up some reference before creating any character. This stage is very important and must NOT be over looked.
Once I am happy with my reference collection, I would then head into ZBrush and start creating the character’s head. Starting out with a basic ZBrush sphere, doing a rough sculpt, and refinements for topology creation.
I use TopoGun for topology, because it's one of the best topo tool out there that fits my workflow. So, export out the high resolution mesh from ZBrush, and use it as a reference to create new topology in TopoGun.
Once the topology is complete, you would bring it back into ZBrush to project the details onto the new topology. Sometimes the projection acts a little funky, so you might want to keep that in mind. Try not to add to much detail on the mesh with no topology, ONLY the newly created topology mesh. It’s a good idea to take that newly created mesh into your 3D package for refinements, in my case, that would be Maya.
The same process that was used for the head, (from ZBrush sphere to sculpt out geometry) would be used for the other parts of the body. So overall, everything should look more like this, with new topology and projected details. Also, UVs need to be layout as well.