While it is focused on real-world lighting techniques, there are principles in this article from the Eejit’s Guide to Film-Making which translate well into virtual world filming. He covers some typical light placement techniques (including an illustration of typical 3-point lighting), and talks about reflectors, colored light, and special effects. It’s a good introduction to the topic, in down-to-earth terms.

The overall Eejit’s Guide has several other articles on filmmaking topics, worth bookmarking if you’re new to this thing.