Work your way around your mesh in ngon strips converted into polygons, as outlined above, and then merge the vertexes of these strips together. (Make sure you don't have any stray vertexes or you'll have a little clean up to do at the end). (image 12)
Once you've spent time doing all of this you should now have a new mesh with better topology. Now I'm not going to kid you and say this is a really interesting job to have to do. In fact it's mind numbingly boring after a little while, but its well worth the effort. Take my tip and stick some music or TV on in the background while you work.
Once we're finished we'll have a re-topologised model that will be easier to rig and use in other applications and with any renderer. If you're so inclined you can also import this re-topped mesh back into Zbrush and get even higher detail out of it, but that's not the purpose of this particular tutorial.
Once finished you can even use a shrink wrap script or plug-in. Working this way you can subdivide your model and each time shrink wrap it to the high res mesh. This way you can end up with exactly the same detail without remodelling the model.
If you're using an application like XNormal that can create normal maps from maps with different topology you can even make one with a low polygon count for rigging, and another with all the large and medium detail and use these to create your maps.
You obviously want to do a good unwrap at this point before exporting a thing, what sort of map you produce depends greatly on in house styles and requirements and if it's a game model your producing or something for animatics or films. Another tip would be to try and make sure it's as easy as possible to do work in Photoshop on it, even if you're using another app for your texturing, there may well be times when you need to fix a few things in Photoshop.
You can of course take your model back into Zbrush or any other application for texturing (or even adding finer detail) with this re-topologised mesh. How you take it from here is up to you and your pipeline. You can see the final re-topologised base mesh of the dragon's head I've been using to outline this method below. (image 13)
Notes about other apps
Obviously Maya was used for this tutorial as its probably the biggest pain in the backside to use. Any application that allows you to draw polygons on the surface of your high res mesh will do the same job. Users of 3D Max may want to look at the 'Polyboost' plug-in as it has features that make the job a whole lot easier. It includes a 'topology brush' feature and a whole host of 'polygon strip' features meaning you can paint your poly strips straight onto your mesh with no messing about.
Other apps have topology brush features such as Modo and Silo. Although I would still not be too tempted to draw your polygons 'blind' in these without your edge loop texture as a reference. What application you use is really up to you as most are capable of this workflow or slight variations on it. Although to be frank whether you wish to buy either plug-ins or an app with a topology brush feature just for 're-topologising' wouldn't be my first choice to be honest. Once you understand the approach to the workflow it's portable to most applications
So I've given a handful of ways of doing this in some applications and you should be well on your way to being able to model without the worry of edge loops or topology. If your used to modelling with good topology it can be extremely freeing to just 'go for it' and model by the form alone, it can produce fast and effective results that would take longer normally. The idea of not having to work out how to get rid of that 'problem 5 sided Ngon that messes up the nice clean topology whenever you sort it out' makes for a happier easier modelling life