No one can tell you how to DM. It's more an art than a science, really. Game design and GMing are different animals and being great at one doesn't always translate directly to the other. That said, experience is the best teacher: GM and enjoy it, the good with the bad. The more you do it, the better you'll get. I've been at it over 30 years, since 1st ed AD&D (after the little brown books, but I have those, too.) Here are a few things I'd say throw in the back of your brain and let simmer-- some are personal playstyle issues, so take them as you will. No campaign is written in stone. Don't allow the rules to stop the game more than necessary. If a rule bogs the game down, make a ruling and run with it. (And then make a note and look the rule up after the game). You don't have to be perfect or right all the time as GM-- players will respect this type of honesty more than stopping for 30 minutes to find a rule or simply asserting dictatorial power. The more you GM, the more you'll be able to make these on-the-fly calls more reasonably and even the best GMs have to do this occasionally or stop the game mid-combat to find a rule. Sometimes, you can make a ruling "until I can look it up." I don't go retro after that (if I was wrong, we play it from once the rule is found the right way). Allow players to do what they reasonably can do-- I'm with the say "YES" group in 99% of cases. Impossible things are attemptable, but may require a nat 20. Most things are already covered in the rules and players can find their own flaws in their plans (I DM'ed a paladin in full platemail who tried to jump a 10-ft pit. The rules did the rest). Allow players to play their characters as they feel they want to (The Hand Incident, anyone?), but let them expect NPCs to behave they way they naturally would- don't let the players abuse the NPCs just because they're players. Also, watch out for 'the penguin with cymbals'-- players who will push your willingness to inforce "suspended disbelief" to keep their characters alive. I only warn about this one because one of my best gaming buds is just such a penguin, who will walk up to a sleeping polar bear and smash the cymbals repeatedly. I've killed him more than any other player, not through vindictiveness or rejection of his plan, but through the dice-- and he knows it's coming when he starts pushing the bounds of reality or stirs up an anthill full of giant ants with a 40-ft move when he's a 2nd level dwarf with a 20-ft move....which he did solo, away from the party.... DON'T predetermine the outcomes of the story. Don't depend on any NPCs to make it (or PCs for that matter). While the overall direction may be something you steer them towards, let the story unfold on its own. Players are inventive and crafty and funny-- they will reward you with unintended consequences of their own actions without you needing to do much more than give them the rope. Things you think they'll blow through in 10 minutes make take them an hour and vice-versa. Let them PLAY, and you DIRECT the rest of the cast and the setting. I like to think that I get to enjoy the story as much as the players do-- I may know what's behind the next door, but I don't know how they'll respond: kind of like watching your favorite action heroes on a new adventure-- you know their mannerisms and how they might respond, but they'll always do something to make you go "wow!" I enjoy being the audience in their movie, to some extent. I roll all dice in the open- death happens. That's what resurrection is for in some games and you can always make a new character. I don't like fudging dice because, as a player, I don't like being fudged on, either to give me something I don't deserve or to whack me when I do what makes sense. I let the dice fall where they may. This one is highly selective, and different GMs play this differently, so find your own happy medium. Don't be afraid to House Rule. Stephen S. points to problems with healing (something I've house ruled on in most D&D games I DM). Don't use too many House Rules, otherwise you confuse the players, but use ones to fix things that don't work for the way you want the campaign to run. Some people get house rule happy-- basically, remember the rule of "if it ain't broke, don't fix it" rather than trying to house-rule "cool" things. And a piece of advice for exposition-- find a way to get the players involved, so you're not talking to them but with them. Supply them with little pieces of the puzzle early and then, when exposition hits, let them try to figure out how their piece fits with what you've revealed. Some exposition can be handled away from the table (handouts/emails/forums here on roll20/etc), providing a great ending/starting place for specific games. If the players get to the wise wizard and ask the magical question ("How many licks does it take?"), and the wizard has a big exposition, let the question be the game ender, post/ send out the wizard's spiel away from table-time, and then let characters start by asking follow-ups. If it's history or political stuff, either post it somewheres or send it to the caster-types and let them disperse it as common knowledge to educated people in the land. Find ways to have the PCs interact with the information and not just absorb it.