Have you ever looked at photographs and wondered how they were lit? Strobist diagrams can help after the fact, but what about before: how do you know how to get the look you want? Consider a cinematography technique: lighting your scene one light at a time.
In a perfect world, we would always shoot with perfect light at the right time of the day. But reality is different. We often have to shoot in terrible light at the wrong time of day. What to do? Create your own reality, or in this case, create your own light.