Prioritize Your Character Design by Using Retopology Tools
Automatic RetopologySome applications have methods for automatically calculating an optimized edge flow based on existing details. Both Mudbox and ZBrush have methods for achieving this. Typically you'll take your high resolution sculpt and then choose a target polycount. You can also change settings that will allow the program to adjust the polycount density based on the level of detail in specific areas. There will also usually be some method of guiding the topology. It's still calculated automatically, but you can draw out guides on top of the model to suggest the direction of the edge flow. The downside is that you can't get complete control over the topology with this method, but it does have the advantage in speed over manual retopology.
In manual retopology operations, the high resolution model will be set so that new points can be drawn directly onto its surface. Then these points, edges, and polygons can be placed and configured manually based on the final detail, automatically snapping to the surface of the underlying model. This workflow allows for a very optimized and custom result without a lot of wasted polygons, but it can take some time. Many 3D applications now have support for manual retopology operations.
Once your new topology is generated, the final step is usually baking out maps like color texture and normal from the high resolution mesh to the new low-resolution topology. For now, technical considerations like topology and edge flow are still a concern for 3D artists, but by retopologizing your finished models, you can put your initial focus on the look of the model where it belongs. To put these different techniques to the test check out Retopology Techniques in Maya to get up and running with retopologizing your 3D models.