Another of my posts on RPG.net's forums. Re-posting it here because it's long enough and doesn't really need the forum thread's context to make sense.

There are a few different kinds of people that might join a first session in a game. The situation is different for each, but for many of them /how/ you introduce them to gaming doesn't make much difference to whether they end up being gamers -- just to whether they ever want to game with /you/ again.

1) People that know about RPGs, are interested in the idea, but have never played before. If you give them a bad first session they may decide they dislike you, your friends, and possibly the specific RPG you tried to introduce them to, but they're likely to go on to find another group of nicer, saner people and play a different RPG, rather than quitting the hobby altogether.

2) People that only aren't RPGers because they haven't played in any. Perhaps they play MMOs and videogames and such, read fantasy and science fiction, etc. but have never encountered polyhedral dice. It's possible to make a bad first impression with these people and have them give up on RPGs, so handle carefully. Still, these people are usually open enough to the idea that they'll assume a bad intro is your fault or the game system's, and whether they ever get into RPGs is sort of dependant on whether someone better offers to run a game for them in the future.

3) People that don't really care about RPGs, but are open to trying new things. Usually they won't be really engaged in the system mechanics, or even the setting or roleplaying opportunities as such. I've had good luck with a lot of these types, though: sometimes the social aspect of playing with friends gets them into the game and keeps them there, sometimes the opportunity to gain cool powers for their character or do impressive things gets their interest.

4) People that don't care about RPGs, don't like the idea, and are only at the session because someone dragged them there. This honestly usually doesn't work out. I've seen it go well maybe one time in six, usually for rules-light games with lots of action and laughter and minimal geekery. Otherwise, they'll leave the game wishing they hadn't come, and they're not likely to look into doing any more gaming in the future.

For all of these people, the 'how do you properly introduce someone to the game' boils down to: don't be boring, don't be creepy, and don't be rude. The latter two are easy to follow (or should be, anyway, if you're not just naturally rude or a creep) but the former can be tough, as everyone finds different things boring. People that love systems will be bored by rules-lite games, people that love roleplaying might be bored by especially mechanical systems, people that love power fantasy might find gritty settings dull and depressing, etc.