So, I get asked a lot about how to topologize a character, and I wanted to share some things that I've learned with a reference/guide for general anthropomorphic characteristics for people. I have provided the blend file for download here.
I've made an outline of a general anthro character with important loops highlighted that I've found are useful to build a character around.
What do you mean by loop?
Simply a loop is a ring of faces that can be cut into cleanly (ctrl+r).
Why these loops?
These loops are placed at high deformation areas that assist when rigging for a character to animate correctly. When a part of the character bends a lot, you need more topology to support the motion. Additionally, sculpting with particular loops encourages the features of a character to not warp as much (visible tris and other weird artifacts).
How do I create the space between the loops?
The topologists bible is all about conversion. Some loops have more edges than others so we use techniques like this to bridge them.
This process is iterative; You can continually decrease your edge loop number by making another loop using the same conversion processes. When you bridge like this, you must put a spacer 1-1 face connection between your conversions on the same loop or you will create a spider.
What's a spider?
A spider is a vertex with more than 5 edges connecting it. We do not like spiders (topology spiders, not cute anthro arachnids, love y'all) because they cause artifacting in shading and are general bad practice.
Quads Quads Quads
We love quads as they allow for clean subdivision surface applications. You may run into a situation where you have a 1-2 conversion for face, this always results in a triangle. The easy solution is to add an edge to one of your loops. You may have to get creative and make concessions elsewhere.
What if I miss a spider?
You can use the select similar tool (shift+g) in edit mode after selecting a 5 edge vertex and set it to greater in the bottom left of the viewport with wireframe view to find any problematic areas. You can do the same with face selection (3) in edit mode to find n-gons or triangles.
How do I fill in the loops themselves?
You can use ctrl+f -> grid fill a selected area with quads. You can adjust the settings in the bottom right of the viewport. If you get an error, make sure the loop is closed and that it has an appropriate number of edges, an easy fix is to add a single edge to the loop and it will allow you to grid fill.
Just a dash of symmetry
If you want to avoid spiders and maintain model symmetry, your model must contain a continuous edge along the center. This means 2 loops must be dedicated along this edge in the center that follow the outline of the character. This loop goes along the center of the face, the tail, the belly, the neck, and whatever other parts you have centered. I point this out as this is not visible in the reference guide because shapes of characters vary widely.
Creativity and Experimentation
Try different loops than these if the character supports it. Tentacles? Loop that base. Unusual eyes? Find the loops for your brows and eye sockets that work for you. Different number of sections for fingers and toes? Cut loops or add loops. Circles and ellipses are your friend. Robotic characters? Make an angular loop. In fact make as many as you want. Loop to your heart's content.
UV Unwrapping
Good topology supports good unwrapping, having clear delineations of areas makes it easier to see spots on a character that can be cut up for texturing.
Rigging
Good loops also help you determine where to put bone joints when rigging. Placing bone connections at elbows and knuckles will net you better deformation.
I hope this helps you feel not intimidated by topology and that your artistic vision is possible.