My first bit of advice would be to only add topology where it’s really needed to capture the form. Otherwise you end up with many unnecessary edgeloops. And try to keep your quads evenly sized/spaced for a decent sculpting mesh. Also, for something like a humanoid head it can be beneficial to place the primary edgeloops first: around the eyes/mouth/ears and then join up those areas always keeping in mind the number of spans(edgeloops) in each area to make connection easier. Also, of vital importance is understanding edgeloop termination and placement of 3 & 5-edge poles. Zbrush isn’t ideal for reorganising topology as the creation of n-gons is illegal, so painting a topological template is very useful(see below) It has been made easier though with the introduction of Zmodeler brush in 4r7. You can for instance use the ‘insert edgeloop’ tool (alt pressed to remove an edgeloop)
It’s a bit of an in-depth topic to discuss in a post but I highly recommend studying other artists wireframes. There are many available to view on google image search.
Also, a good idea is to polypaint your topology onto your model so you have a guide to create to. This can save you a lot of time and heartbreak and is a great learning aid to understanding topology flow without worrying about messing up the topology and spending a lot of time fixing it.
Here is a great resource to understand facial topology;
Hippydrome
