While cleaning up my system I came across this old video by another modeler. There are many ways to introduce new flow and geometry into your mesh. Most likely, Triangles and nGons will be introduced when you use Knife, Loop Cut, and many other tools. However, if you start with a Cube and plan out your extrude(s) and spin edge carefully you can have a mesh that is all quads. This three operations: Extrude, Spin and Tweak seems to be sufficient in most cases. This type of mirror editing seems to work flawlessly in LightWave, but Blender? Nope. It doesn’t work perfectly and strange things do occur. As of this writing, Blender doesn’t do well with this Combo operation in a single-mirror editing mesh.