Lighting levels for Quetoo is very simple; easier than lighting them for Quake II. The BSP Compiler's lighting phase performs only direct lighting, without radiosity, but also calculates light direction values for per-pixel lighting. The following guidelines generally produce the best looking levels and the shortest BSP compile times:
Use a small ambient_light value in your worldspawn entity. Values less than 0.15 0.15 0.15 are usually appropriate. Tune the value to reflect your sky environment color.
Use sun_angles, sun_color, and sun_light for levels that have sky surfaces. Even if you have a night sky, a small amount of sun_light gives you ambiance and atmosphere for free.
Use light-emitting surfaces (SURF_LIGHT) sparingly. Point lights are much more efficient for the BSP compiler to process, and will generally produce equal or better looking results. A proper use case for SURF_LIGHT is a long, thin strip of contiguous light sources.
Place lights only where you have actual light sources. Don't drop point lights in "mid air" where there is no light source. You're better off placing point lights as close to their actual light sources as possible, and making them very strong if you need to cast light on a floor that is far away.
Keep it simple and realistic! Fewer, stronger light sources will generally look much better than numerous, weak sources. Avoid adding more than one point light for each light source. Keep the point light close to the light source brush.