Guidelines for a Base Mesh
• Always use quads
If you must have triangles, hide them away in an armpit or on the bottom of a foot. ZSpheres are great for quadrangulated meshes (though hands and feet are difficult to make using them).
• Don’t Worry about the Shape
Your model doesn’t need to be anything spectacular to start with. The most important thing is that you have the quads and edges where you need them; the shape and proportion can and will change. You can see from the humble [base mesh] that all the magic happens in ZBrush. It is so good at moving points and changing proportions (TransPose) that we only need to start in the ballpark and then progressively refine as we go. Have a good laugh at how mediocre this base mesh is, but remember it is just the starting point.
• The lower poly the better
A very low-resolution base mesh is great for making large changes to your sculpture by pushing, pulling, or moving single vertices at a time. Often for production work I use a very low-res mesh to start my sculpt, but export SubD Level 1 or 2 for rigging and animation.
• Edge loops do matter
While not critical for digital sculpture, it is good to get in the habit of putting decent edge loops on your model, they do help. A well edge-looped model will require fewer polygons to represent form and you will never feel like you are fighting against misaligned edges. The edge loops should broadly flow along muscle groups and in the direction of deformation. I also use specific edge loops to represent critical skeletal landmarks. I would, for example have an edge loop that distinctly represents the clavicles and others around the hips that represent the iliac crests.
• Make ‘square’ quads
Do not make long rectangles. When subdividing the mesh into digital clay, rectangles with long polygons turn into long micropolygons which are awkward to sculpt on and destroy the feel of your brushes.
• Strive for quads of equal size
As much as possible avoid over detailing regions of your base mesh. Avoiding areas of small details can save hundreds of thousands of polygons when the mesh is subdivided, often allowing you to get another subdivision level out of your available memory. Remember: subdividing a single polygon eight times results in 65,538 polygons. (And who wants this many polygons underneath every fingernail?)
Of course, if you are modeling for production there are different requirements but efficiency is still important. Also, if you know you are going to have an area with a disproportionate amount of detail, you will want the base mesh in this area to be proportionally denser. (Or you can use ZBrush’s HD geometry.)