Before jumping into the deep end with modeling, let's take a look at some modeling theory in the shallows.
Before we start modeling, I just want to touch on some basic but essential polygonal modeling theory. If the geometry needs to be taken into a sculpting package or animated, a clean mesh is crucial. On top of this, well-executed topology produces fewer artefacts during render time. In short, a polygon in time saves nine.
Step 1: Quads v Tris v N-gons
So what is the difference between a quad, a tri and an N-gon? Well, a quad is any four-sided face, a tri will have three sides and an N-gon will have anything more than four.
Out of the three of these, it is highly recommended that you try to keep everything in quads. Generally, they subdivide more predictably, deform better during animation and you encounter less texture distortion.
If you need to use tris, then it is best to try and hide them in places where they are less likely to be seen, such as under the groin or armpits on a character.
N-gons, on the other hand, should be a no-go zone. When subdivided, N-gons can cause pinching in the renders and can be a pain when weight-painting during the rigging stage.
Taking a model that is predominantly made of quads will also transfer better to packages such as ZBrush and Mudbox.
The joys of quads and the terror of N-gons
Step 2: Uniform Geometry
Uniform geometry means that we are trying to keep our polygonal faces as square-like as possible, and space them as evenly as we can across the surface. Doing this makes weight painting at the rigging stage easier and leads to better deformation during animation. You will also get less distortion when applying textures, although the importance of good UVs will also be a factor in this.
To help you get the geometry uniform, Maya has the wonderful Sculpt Geometry tool. Setting its Operation to Relax should allow you to iron out the edges.
Using the Sculpt Geometry tool will help to even out the edges of your model