@evan rules are a (imo very weak) social construct, and the most important thing is everyone has fun. The players are the ones who bring the main characters, conflicts, and determine the general direction of the story. The role of the GM involves a lot of improvisation to make it all work, and provide all the parts between (like the world).
@evan your players will have different degrees of participation that they're comfortable with, and your extroverts will hog the spotlight without thinking about it. I think it's important to find opportunities for every player to show off (without pushing unwillingly out of their comfort zones) so the game isn't just focused on one extrovert
@evan I find it helps to have a general idea of what might happen in a given session, but don't get too attached to your plans happening the way you want them to. If your players really want to send things off the rails in a way you have no idea how to handle, you can call an intermission to give you time to think over how you want to handle it.
@evan if you find you're bad at coming up with new ideas on the spot when your players inevitably surprise you, there's no shame in borrowing ideas from familiar media. Pull in stuff from books or movies or such that you enjoy.
@evan Also the classic writing advice of "if you're stuck have someone bust into the room with a gun" doesn't actually work all that well for GMing in practice, because you'll be quickly made to answer a lot of questions you don't have answers for on the spot.