what type of lighting are you interested in? Are you looking for lighting that improves your realism? or are you looking for lighting that helps you to create different art styles?  There are so many types of light settings and positions that you can use with lighting to create different types of artistic looks.

The type of lighting that you use all depends on what you are trying to accomplish.  I guess it's similar to what JohnDoe said.  Take a look at some real world lighting techniques and some traditional art lighting concepts.

Or you can sign up for a free membership on my site Poser By Design and I can show you some simple techniques that go a very long way to improving your use of lighting on an artistic level. I think I have some Poser 8 lighting tutorial videos that are still available in the members area.  You can look at my renderosity gallery to see if my images have the lighting that you would be interested in learning.