Only thing I have to add to this topic is to realize that you are going to have to improvise from time to time. Being a good GM isn't all about carefully planning your RP in such a way that it can't screw up. It's about having a plan, and being able to keep your cool when things go in an unexpected direction. All Gm's plan (some better than others) but the best can improvise when the situation calls for it. The players [u][b]will[/b][/u] do things you don't expect. That's your cue to evaluate to situation and find an interesting way to get things back on track.