Thank you Manuel, however I will have to disagree with the catchlight statement. The catchlight is there as a scaled down reflection.
Using the theory of "If the eye is painted correctly it will catch the light source from what ever angle" then shading and highlighting is not necessary either because if painted correctly then the clothing would also catch the light source from what ever angle-but it would be out of scale.
What we are doing by painting a minaiture is expressing a period of time and setting. While not necessarily "correct", the painter should be trying to portray a light source in miniature. ie, the figure is painted to depict a man standing in a certain place at a certain time-not to catch reflections from say, an overhead flourescent light in a room it is displayed in. As everything else, the lightsource must be scaled down to the figure.
See Fletcher Clement's depiction of Michaelangelo's painting of the Cistine Chapel. The piece creates a mood and environment based on the lightsource he chose to employ. That is the difference between a technically well painted piece and one that comes to life to the viewer. In reality, most times the catchlight on an eye is not really "seen" by the viewer but causes the viewer to think the eye is real.
The technical term is called "Tromp L'oi" (not sure if that's spelled right) but translated means "trick of the eye".
With figures, we are creating an environment-it's not like a model car or plane in which scaled lightsources don't matter.
But of course, everyone is free to paint as they wish. This method just works for me and quite a few other painters in the hobby.