Running a game isn't hard. Running a good game just takes practice. Like playing a character, the DM gets to play everything on the other side of the screen. Don't be afraid to try running a game. Start small. Maybe a quick two level dungeon. No fancy plots, or long story arcs. Get in there and offer to run a couple people in something that will cover one or two sessions. Make sure you understand the task resolution or game mechanics for a system. How does combat work. How do characters interact with the world. If there are lots of mechanics focus on the bare minimum that keeps the game rolling. When you decide to run a longer game next time you can use more rules or even just make house rules. Yeah Game Masters running home game stuff can just make stuff up. Otherwise attempt to know your audience. Lay out to potential players what your looking to do, whether straight dungeon crawls, investigation scenarios, dark fantasy, or a one shot just to try some new rules out for a game you bought.
