Things I always abide by

Don’t lie to people you’re trying to teach by praising them prematurely. They’ll find out sooner or later, and when they do, they’ll lose faith in you. No need to be a dick about it, but it’s always best to keep it honest.

Same goes for when you don’t know something. Say you don’t know it. You can hazard a guess, but you have to say that it is only your best guess. Either way, it’s usually easier to say you don’t know the answer.