Hi Annet,
In my teens I made light show for bands, and had a truck load of equipment, mostly DIY build, but also old spots from theaters, that I repaired. Long story short, I love light.
As a cinematographer one needs to know light, and that is pretty much my source and passion since long. The main tip I can give, if someone starts out with a three point light, without asking what you like to do, run.
The main problem with setting the light is to start with too many lights. Find images, paintings, movies that resemble the light you like to have. Then find “pointers” that explains the scene. Typically specular highlights give away where the lights are, and shadows of course. In any way, find the mood you would like to have first. If you don’t have that, anything will be guesswork. One can see that on set when too many lights are set up in hope it will work out at one point. Some masters work often with just one. But to make that a rule is also wrong. Again, mood first, than explore how to get there.
Another point is to explore any outdoor or even indoor scene, if you like the mood, find out what is the key. take snapshots and come back later when things have changed, take snapshots again. Compare.
Of course, it becomes at one point technical, you need to know the given light-sources. Since fourteen years I get scene files from people, and I check them carefully each time. I certainly have an eye on the parameters of light, and which one is left on default.
Learn everything there is about Shadows. They are never black, nor do they have a sharp edge normally. Often shadows have a blue tint, and sun light is warmer. IF done just slightly, it feels more right than just white light and black shadows.
Yes, I could go on and on, but I guess these are the base pointers. Quality of light.
Have fun exploring
Cherrs