To be honest, I haven’t seen a great tut on edgeloops that I’ve liked. However, for facial work, I can recommend a book: Stop Starting by Jason Osipa ( http://www.amazon.com/Stop-Staring-Facial-Modeling-Animation/dp/0471789208/). he gives one of the most lucid discussions of building an animatable face (mostly in Maya.)
The trick to looping polys properly is to lay down your loops first. Then build out from the loops, following your mass/muscle flows of the surface. I often encircle the eyes and mouth first, construct the nose to my liking, and then start linking things up by asking myself, how does the flesh or muscle flow from this point to that point and build my polys accordingly. Silo and 3D coat have pretty good tools for doing this by letting you drop down strips. If you have casting experience, you might think of it as laying down thin strips of plaster bandage to follow the direction of the surface flow.
You will be ultimately left with some spots to fill. This is the “puzzle” part that Alex talks about (IMHO) and there you have to look at how you can fill these remaining surfaces in a way that 1) uses the most quadrangles 2) respects the surface flow 3) creates the fewest places where more than 4 edges meet 4) avoids places where six or more edges meet.
Why these criteria? Here’s my take on it:
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Quads are the most table form for subdividing because they divide regularly and define the surface in two directions in a mathematically stable way. (Important for the software representation of the syurface and rendering.)
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The surface flow is what you will sculpt on. Therefore, you won’t end "fighting your topology as you lay details on top of the flow. Most techniques for representing detail deal with the “normal” of the polygons which is a line that sticks straight up from the polygon face. Detail that is askew of straight up from the point on the face tends to “fight” ost projection algorithms.
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Webs or grids of exactly four edges is a very mathematically stable representation of the surface. Points where 5 or more edges meet (I call them stars) often indicates a change in direction of the surface. Make sure that you truly “mean” that change in direction and are not simply filling up a whole.
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More than 5 edges starts to create a “pole” where direction is arbitrary and therefore the representation becomes increasingly arbitrary the more lines that meet there. Think of yourself standing at the north pole with all the longitude lines underneath your feet. Is there an East or West? No. Is there a North? No, you’re at the north-most point. There is only one direction, South! The mathematics of this can get confusing and you’ll see the results if you build up and smooth over a pole on say a basic sphere representation in ZB.
Another way to think about edge flow is think of an ant with muddy feet walking along the surface. To the maximum extent possible, you want the flow of your polygons to move along those lines. You can almost never efficiently do it 100% on a complex surface like a face, but the trick is to maximize where you can, and try to put the areas where you can’t as far from the focus of your sculpture.
Sorry for the long answer, but hopefully this can give you some pointers.
-K