hearditbothways:

Ack, sorry this is so vague, anon. :S As I said in my last “tutorial”, your best bet is probably to find reference or recreate the lighting to the best of your ability, since lighting can be pretty complicated at times!

My process is usually to determine the overall ambient light and how it will affect the subject and environment, and then  determine additional light sources (like your glowstick example) accordingly. The intensity of the secondary light sources depends on the size, brightness, and proximity of the source. I normally don’t add more than 2 light sources, because after that it gets more complicated and confusing for both the artist and the viewer. It’s best to keep it simple at times!

If you want a more in depth guide, I recommend checking out James Gurney’s teaching images and his book Color and Light. He obviously has a way better grasp on this than I do LOL. Virtual Lighting Studio can also be a good guide for lighting on faces, but is pretty limited in what it can do.

Hope this helps out a bit! ♥