So, this is a very very basic lighting setup, but it’s a decent starting point for this scene. I am lighting this using two lamps. First is coming from what I assume was a lamp on the desk. I’m going to say that this is the key light in this scene. I gave the lamp a little bit of an orangish tint to warm things up a little, and adjusted the shadow soft size (2.0) and the number of samples it is using (6). This makes the shadows softer instead of hard edged.
I then added an additional lamp to fill in some of the shadows and make them less dark and harsh. I did this with a blue tinted light and turned shadows off and specularity off on this lamp. There are some realism issues that may be caused by doing this sometimes, but the reason I did this is because I’m not actually trying to simulate another real light source with this. I’m more just trying to create a little ambient light to fill the shadows, and I dont really want this ambience creating its own shadows, or specular reflections, and to my knowledge Blender 2.49 doesn’t have any real great ways to do this. In 2.5 there are better ways of achieving this same thing. Obviously this would be done differently if this was supposed to be a real light in the scene.
In all reality, lighting is a very subjective art. Once you know the basic rules you just have to look at your render and figure out what you need to do in order to make it look the way you want it to look.