I have introduced about 8 20-30 year olds in D&D this past year, but for my 8, I had about 10 failures. It is not easy, but it can be done.
The friends that I was most successful were ones that had been friends of mine for a long time, just never played any kind of pen and paper rpgs. A few were big sci-fi fantasy fans. Two were computer/console rpg nuts. And one was a big MTG player.
In short, if some one is already active in "nerd culture" in some form, it is much easier to get them to play.
Pre-generated, simple characters were the route I used and we played an easy adventure. (Scourge of the Howling Hoarde, but the Paizo Hollow's Last Hope was the one I used with my wife.) After the first adventure, I offered to let them keep their characters or to create new ones at the same level.
Of the 8 I introduced to the game, 4 are pretty regular, 2 are semi regular (very demanding jobs), and 2 grace us with their presence only every blue moon.
The people who were not interested tended to be fearful of stereotypes. (ex. D&D is for nerds and people who worship the devil) One used lack of money as an excuse, despite the fact that we have a few extra phb's stacked around. Most though, were just to busy to commit to play and said that once their kids were a little older or career stabilized might give it a try.
Sorry for the ramble.