A user named Nir posted in another thread about the "Sunny 16" rule, referring to the fact that when shooting in full sunlight, proper settings are usually f16, and then 1/ISO for the shutter speed.
What are some other tips or tricks like this? For example, tricks to photograph snow, or dancers in a theater, or starscapes. Anything really. I hope this question isn't too general, but I think it will be a helpful resource for many.
I'm not looking for tips on photography basics, but rather situational tips and tricks that you have found work really well all the time.