- Top priority: Run what excites you, the GM. The game runs on your brain, so that energy influences every aspect of the experience. In its absence the game will fall apart sooner or later.
- Don't expect your first (or 50th) game to be like Critical Role.
- But if possible, watch/listen to an Actual Play video/podcast for the game or module to get familiar with its content, (one way) how to present it, and ways the players might respond.
- Make your first games "one-or-more-shots"; a one-time thing with the option for a followup session. Don't worry too much about wrapping things up neatly; it's tougher than it seems.
- Run a ruleset and module that's well-organized and easy to reference at the table. If it isn't and you still want to run it, reformat it in Google Docs and print out reference sheets. Prime example of a well-organized and presented ruleset: Old School Essentials. Examples of easy-to-run modules: Tomb of the Serpent Kings, Fever Swamp, Through Ultan's Door.
- Have a discussion about expectations at the start of (or before) the game: what kind of game it will be, how it might differ from games the players have experience with, the "verbs" (what kind of activities you expect the characters to get up to), the tone, content notes. Discuss and use safety tools if there's any question of whether they might be helpful.
- If you're interested in old school style gameplay, which generally emphasizes exploration and creative problem solving over satisfying storytelling or crunchy tactical combat, check out Principia Apocrypha for a bunch of advice.
- Part of why I like old school style games is that they're generally low-prep. Rules are usually simpler, you're not writing a grand, sweeping tale with a personalized character arc for every player, you don't need to know the population of every village in the kingdom or the name of every god. You're just some broke knaves in a dirty hole trying to get find treasure to pay for some armor so you don't get killed as soon as you set foot in the next hole. When the stakes are low, so is the prep; a little goes a long way.
- Unless you definitely want a super-detailed world and/or plotted-out storytelling, you can cut down on prep with liberal use of random tables to fill in circumstantial details on the fly. In combination, they can even produce situations that are more interesting than you'd think to come up with on your own anyway. A superb, cheap, comprehensive source for random tables is Maze Rats (also a great rules-light old school style RPG)
- My favorite note/prep organization app is workflowy.com - I'd be helpless without collapsible, draggable, hierarchical, nested notetaking. That said, it's not exactly effortless to reference or edit while running.
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