What is a good model?

Before starting with the modelling you should have a clear idea of what you are actually trying to achieve. Having some reference images helps with the creation of good proportions which is a very important factor. You should always aim to make your character distinctive. The character must me appealing, strong and interesting in order to catch the audiences eye. For instance, when devising The Simpsons, the creator knew that the bright yellow skin and the unusual design of the characters would grab the attention of the viewer.
The strong topology makes the work of the animator much unchallenging and pleasant. While creating the model it is a good habit to always check for errors like triangles or holes instead of fixing them after you finish. It is essential that you have good edge flow in certain areas of the mesh - usually around the eyes, the shoulders, knees etc. This aspect of modelling matters if you are planning to rig the model for animation because the poorly made model is hard to rig and skin, it also deforms badly when you are animating it.