Lighting placement for environments

VisceralD

So I’m a modeler that was previously focused on characters now transitioning to focusing on environments. So I just wanted to ask the pros on if they have any techniques for placing lights in the environment. Both to be visually pleasing as well as to be functionally affective.

LMP

First, lights should be placed where there are sources, then I sometimes used fill lights to add a little more to important areas. Color and intensity would be tweaked to achieve the desired mood.

Obscura

"First, lights should be placed where there are sources, then I sometimes used fill lights to add a little more to important areas. Color and intensity would be tweaked to achieve the desired mood."
This.

Plus here is a useful doc:
http://www.scribd.com/doc/4063526/Pages-From-TheHowsAndWhysOfLevelDesignSE-Lighting