SSAfam1: Your question will get you a multitude of answers.  It boils down to what type of scene are you creating.  I can get by with 3 lights if I am concentrating on a small aspect of a scene; others may require more to illuminate specific areas and create mood.  Outdoor daytime scenes will require an infinite light and perhaps 1 - 2 fill lights to brighten shadows.  Nowadays IBL is becoming a very important source of ambient light to add a touch of realism.  Again, it is a matter of scene requirements, lighting demands and what you intend to convey as mood and feeling.