I've seen a few different posting guidelines in different games, and I have started borrowing/stealing from them. But I was curious: what are your favorites - as either players or GMs?

What posting guidelines do you like to run? Linky? What have you tried but failed? What do you always make sure to include - and assuming that players aren't really going to read and remember *everything* we throw at them, what is it that is MOST important to impart on them as/before the game starts?