Being a Dungeon Master for a regular D & D game is a whole other level of nerd. If I dare mention it to people most raise their eyebrows, mistaking the abbreviation (DM) for something slightly dirtier. Explaining that it means Dungeon Master doesn't really help.
Nevertheless, creating the narrative framework within which players bounce around is a challenging enterprise, but a rewarding one. I've learnt many things from the process, and been reminded of essential core skills. It's had nothing less than an absolutely positive effect on my writing. Not kidding. I now tend to imagine characters or readers as players in a game that I'm designing.
- Don't lock down. In D&D, of course, the players can throw you a curve ball, and you have to respond off the cuff. Such interactions can cause the most interesting branches of gameplay. You have to remain open to whatever left field idea a character comes up with. Characters are capable of making unlikely or interesting decisions. It's what makes them unique.
- Don't relieve tension. Solving a puzzle? There's goblins hammering on the door. Taking too long to chat? An orc's passing by and he looks pissed. Keeping the pressure on players stops them from dithering and slowing down the game. The same is true for story-telling. Erring on the side of going too fast is always much much better than going too slow. Boredom is the last thing you want to inflict upon players and readers.
- Play music. Atmosphere is key, and it can do over half of the work for you. Play music when writing, but also fiddle with the environments that you're writing about. A few details make the whole thing come alive.
- Don't be nice. Character's are the most interesting when they have a secret, or are forced to tell a lie, or trapped into a situation that looks impossible. The player/reader may whinge about their situation (thinking of George R. R. Martin's constant killing of characters), but the reader will keep going. Be mean, keep the pressure on. That's when things get interesting.
- Short game's a good game. Why take eight hours when you can take three? Don't write too much. The reader will pick it up. You can't do all the work for them.
- Rules can be bent if it means a better story. Fudge dice rolls to get to the point, scratch numbers if the idea is too good to be dismissed. Reward creativity in your players by making sure it happens. Same is true for story. Always always always obey the rules of your world, and then choose the moments to bend them.
- Understand why you're in it. Enjoy the moments that are fun. The moment where your players put together a puzzle that changes a story completely, that you've been designing and guiding them through for the last four hours. The short thrill is the only reason why you would bother putting this much work in. Enjoy the successes when they come up. Bypass beating yourself up over the failures.