When thinking about lighting, the best thing you can do is closely study real-world lighting situations. Thinking and analyzing how light works around you will help you understand how light works and help you see the potential of the tools you have available to you in a 3D environment. I can't say this enough, but you have to remember that the lights you create in 3D are at best a very simplified and limited representation of real light. In order to simulate real-world lighting, you really have to understand the tools you have to work with and find creative solutions that give you the result you are looking for.
Take a photo and spend the time to analyze the lighting scenario taking place in the scene. Choose an area outside that you can visit and take notes at different times of the day, when it's sunny, overcast, raining, and so on. Focusing on a familiar area will give you the chance to really document and analyze the subtle changes that take place.
As you walk around during the day (or night) look not only at the lighting around you, but also for the light sources, and think about how they are influencing what you are seeing. Look for color, direction, specular highlights, intensity, and so on. This goes back to reference and its ability to provide you with information you would never be able to imagine on your own. Look at film and artwork that catches your eye and analyze what is happening with the lighting. The key to developing your skills as a lighting artist is to rely on your ability to observe and re-create what you see around you using the tools at hand. In the next chapter, we will take these ideas and apply them even more specifically to lighting for games.