What it takes to be a Good GM
Having followed and participated in this thread... And from personnal experience I can safetly say that there is a guide to being a Good GM, anyone that follows these rules conciously or not qualifies, whether they consider themselves the worlds hottest GM or merely an OK one.
Rule 1 - Have fun and share it with your players.
You are all gathered for a social event, chances are you are all friends outside of the game too. So the key is to tell a story and share it with your friends allowing them to participate in the telling of a story.
When it comes right down to it. Thats the only rule. All the rest about using rules, keeping canon, knowing the world and background are merely fluff. At the end of the day, any fool with an imagination can be a great GM, and wouldn't even need rulebook or dice, although a pen and sheet of paper might be useful! ;)