1) The bigger the surface area of the light source, the softer the shadows. The closer the light, the bigger it becomes relative to the subject.
2) Inverse square law says that if you double the distance, the brightness of the light falls to one quarter (which is two stops darker).
3) Angle of incidence equals angle of reflection, which means that light bounces off a surface at the same angle that it strikes it, like a snooker ball off the cushion.
4) Less is more. Generally speaking, the simpler you can make it, ie with the least number of lights, the better it will look without too many confusing shadows and conflicting highlights. For example, where appropriate use a reflector instead of an extra light - that sort of thing.
If you put those fundemental principles into practise, you've got it pretty much sorted