THERE ARE NO RULES AS LONG AS NO HARM CAN COME TO MAN OR GEAR
Do no harm, step back and make sure that you’re not getting “in the way” of a good sound.
Change, don’t “tweak.” No one hears tweaks.
If someone asks for the vocal up 0.2 dB, laugh as if it’s the funniest joke you’ve ever heard, burst out laughing later and quote the joke. Repeat as needed.
Don’t use brick wall limiting on your mix for any reason other than because you like it. Good mastering engineers can make it louder/better than you can, but they can’t remove an inappropriate decision.
If in doubt, don’t.
If it’s “right,” do it.
Be ready. The “wrong” gear choice that’s ready beats waiting past the “best available performance window.”