How to Topologize a head in Zbrush
Once you get the roughed in form of the Head done it is now time to Re-topo the head for better structure. This tutorial will show you how to use the topology tools in Zbrush to do this. This lesson follows "shape a human head in Zbrush" but is not necessary to do if you just want to learn topology tools.
NOTE: This link is to a Flash version of the first 5 minutes of this 60+ minute tutorial. A download link is provided on the page for the full WMP tutorial.