One of the hardest parts of DMing to master is the art of improvisation. It requires skills and training which unless you are specifically an impov actor or comic, you are unlikely to have. Personally, I have had a little experience in acting, and love improv, and have learned over the years to translate this into useful ideas while sitting behind the Dungeon Masters screen.
The first most import rule of Improv is ‘Yes, and..”
As a DM you may have read in the DMG or online that you should say yes to your players, this is a shoot off of the old improv saying ‘yes, and..’. To move the scene along, to make things flow and keep it fresh. First, you agree. “yes, there is a secret compartment at the bottom of that coffin” and then second, you elaborate.. “and it is filled with an asymmentrical pulsating red ruby which begins to grow hotter and hotter as you hold it until finally it…”
You see isn’t that more interesting than “no, there are no hidden compartments” or “there’s nothing inside but dust”
Your players are a valuable source of inspiration, they may be joking or saying things randomly or searching all the wrong places but that is perfect fodder for you to throw in something which A) they didn’t expect, and B) you didn’t expect either!
The second tip or trick that I like to use.. is called the The Improv Pool.
The Improv Pool, is something which I use during games and even conversations to keep things fresh and rolling. The Improv pool is a consortium of things, characters, ideas, scenarios, phrases and actions, which is just floating around in my head. Essentially, you read books, watch movies, listen to music, play video games and you take the most interesting people, places, and things you can find, and remember them. Then when you need something at a game, you reach into the improv pool and pull out the first thing you remember. The beauty of it is.. it won’t be perfect.. you will never remember it exactly as it was.. and thats the best part because instead you fill in all the gaps.. and when your players ask questions.. you flesh it out right there on the spot and now you have something which is unique to you.. and your game. Try adding a bunch of things to your improv pool and seeing how it works out for you.
Lastly, if you want to improve your improv skills, watch the pros, do as they do, and be comfortable doing it. The best source for hilarity and great improv is a tv show called ‘Whose line is it anyway’. These guys are improv genius’s, it is quite inspiring really plenty of good material to remember for weird or odd scenarios to add to your improv pool.
And as always, practice. The more you do it, the more comfortable you will be, the easier it will become, and the better you will get. How do you practice? Tell a story and make it up as you go, ask for names and characters from whoever you are telling it to. Run a DnD game with zero preparation, just set the scene and roll with it from there. Play improv games with your friends to hone your skills. These things will all flex that seldom used muscle and in no time you will be thinking on your feet as fast as Ryan Stiles and as inspiring as Chris Perkins.
Good Luck and Enjoy!
For more DM advice check out the DM Experience articles by Chris Perkins at http://wizards.com/dnd/Article.aspx?x=dnd/4dmxp/20120823