I played a one-off game with my cousin when I was 12 years old (too many years ago now). I had never heard of it nor had I any particular interest in it when he mentioned it. I gave it a try anyway. Something almost magical happened during that game, and a hobby was born. Ive been playing ever...
I might ask them if they have an idea of what they want to play and then pregen characters based upon what they said. Those that dont know/care what they play can fill in the gaps with random pregens. This can be fun for a great introductory adventure. After this, however, I would seriously...
One of the great things about 3E and revised is the fact that we players get to level up a little bit faster than in the old days. Its nice for me to be able to get some tangible character advancement every few sessions (I know, I know. Roleplaying itself is a tangible reward. blah blah blah). :P
I get too attached to my characters to NOT want them raised. I find it hard to get a roleplaying "rythym" down when I have to switch characters too often.