A person who has not yet been indoctrinated into the realm of role-playing games (in the store, I call them "muggles") is standing somewhere near the Vampire: The Requiem shelf, and begins to look at the books. Usually, if someone has been standing there for a while, I'll ask them what I can grab for them (far better sales technique than "Is there anything I can help you find?" for the retail people out there). If they tell me they're browsing, I suggest that they should "Feel free to buy everything you browse past!" and leave them alone. If they ask me about the game, or role-playing games in general, I give them the briefest possible explanation I can.
Muggle: So, I've never really played one of these games before... What's it like?
Me: You ever take drama, or seen Whose Line is it Anyway?
Me: Cool. It's like improv theater with rules and dice.
For some people, this is enough. They get an idea of what it is the hobby is about, enough to make a choice on whether or not this is something they want to be a part of. It's an improvised storytelling medium that involves some rules, and a system for determining arbitrary outcomes in a fair way. Cool. Moving on.
Others begin to ask more questions, and that's when I'll start getting into a bit more detail. You have a "character" who you portray, describing his or her actions and speaking for them. There is a "director" who tells you the situations in which your character finds him- or herself, and who controls the supporting cast. The rules are there to give you an idea of the sorts of things your character is good at, and to handle any situations that might come up; for instance in a Vampire game, the rules tell you how sunlight will hurt your character, and how strong your character is.
For some people, this is enough. They get an idea of what the hobby is about, enough to make a choice on whether or not this is something they want to be a part of. Others will ask more questions, and I'll answer them, and the process continues until the person I'm talking to has enough information.
I know I've said enough when the person I'm talking to has stopped asking questions.
This is a technique that I've used to describe role-playing to an insane number of people. I've been playing these games for coming on twenty years, and I've played with hundreds of different people in that time. Most of the time, I didn't meet those players; I made new players. I told them what the hobby was, I answered their questions enough to give them an idea of whether or not it was something they'd like, and if it was, I'd run a session or fifty for them. This is part of what makes me a successful salesperson in the games industry (and it's why I've played D&D with as many women as men).
The only time I see problems with this approach is when there is another gamer standing around the same shelves. I'll ask the muggles what I can get for them, and they'll ask questions. I'll answer them briefly, and if they don't ask further questions, I'll leave them to their choice. Almost without fail, the gamer customer will feel the need to chime in, and it is almost always in a way that is unwelcome and intimidating.
Gamer: That game is awesome.
Gamer: Yeah, man. You can be like, twelve different kinds of vampire, and they each get special powers. Like my guy has Protean, which means he can sleep in the earth without getting hit by the sun. And this one time, a bunch of werewolves were coming after him, so he had to sleep there for three days and he almost went into torpor.
Muggle: (putting down the book) Okay...
The problem here is oversharing. The reason the game is cool to you is not the reason that someone who has never played a role-playing game is going to want to try it. A person who is going to pick up a role-playing game for the first time is interested in only a few things: is it fun? is it easy enough for me to learn? will I get enough use out of it for the cost that I pay? and is it fun?
Fun is a different thing for different people. Some of us honestly don't like improv theater with rules and dice. Some of us don't want to hang out and make up stories about people who don't exist and tell them to eachother. And that's okay. But keeping it simple, and telling people only as much as they need to hear to make a choice, is the easiest way to get new people into the hobby. There is a lot of information out there, and much of it is intimidating and strange. Just because you and I know what Auspex does (or Sneak Attack, or Glitterboy armor, or a wireless netjack, or whatever), doesn't mean that a person who hasn't played wants to. Sharing your own experience with the game might help someone who is on the fence decide to get into the hobby, but unless you're invited to share, you could just as easily be turning someone off from something they would have really enjoyed had you remembered a few simple rules.
- Basic is better: Give someone only the information they need to know first. Role-playing games are like improv theater with rules and dice. This is my standard, go-to line when telling muggles what the hobby's about.
- If they're not asking questions, it's better to let them make the choice on their own: People who ask questions are interested. People who want more information will request it. If you're offering information that hasn't been asked for, you're probably sharing a bit too much.
- Only answer the question they've asked: Examples are not needed. Specific rules from the books are not needed. Telling muggles the rules of the game is not telling them about role-playing games. Telling muggles about your character is not telling them about role-playing. Telling muggles which edition of Dungeons & Dragons you prefer, and why is not telling them about role-playing. If they ask "So, okay, you have a director and some characters, but how do you know what to say?" just answer the question.
- If you think you can't handle that, let the person behind the counter deal with it: Get his or her attention if you need to. Getting people into this hobby is my job. I've been doing this for a long time, and I'm good at it. My bet is that the person standing behind the counter at your Friendly Local Game Store is probably pretty good at it, too.