Scartol: The more I teach beginners, the less use I have for the 9x9 board. It feels analogous to teaching someone how to play chess using only pawns. The complexity of the board's regions and groups is what makes the game interesting for me, and beginners get none of that on a 9x9 -- it's all corner play. I moved to the 13x13 as soon as I was able, and I encourage my students to do the same.
Stefan: I think I know where you're coming from. Most beginners in our club don't play on 9x9 very long, but do on 13x13 for a while. I'd say 9x9 is for getting a working knowledge of the rules, 13x13 for getting a working knowledge of the basic techniques and concepts, and 19x19 for finding out you'll never have a clue.
Chris Hayashida: Sorry, I didn't mean that the beginners should stay on a 9x9 board for very long. I should have written "smaller boards" instead of "9x9 boards." Usually our beginners start playing on a 13x13 within two or three nights. (More than anything, I think it's a lack of boards that's causing this, but the AGA will soon fix that. :) However, I do think that simplifying the game does appeal to some people. My comments above apply to 13x13 board as well.
Our club is a little different, since we meet weekly in a local coffeehouse. Many people come to the coffeehouse, see the game, and decide to start playing. I think the simple rules attract potential students. It also helps that you can get several games in the course of an hour. These people are a little more intimidated by the 19x19 boards. I think it's a different situation than a "real" go club, since people visiting there would only be coming by if they wanted to learn to play anyway.
Gabaux: I was teaching a couple of newcommers to play go, and some of them became definitely stronger players then me :-)). My idea was to teach the minimal theory first, only the rules and the calculation of liberties. The first-hand experience is very important. I urged them to play a lot of games in a rather short interval of time to get as much practical 'feeling' as they could. Sometimes I let them win, but not too often, to learn how to exploit overplay, how to recognize bad shapes. I have found this approach very efficient.
mgoetze: And what's wrong with giving beginners a large handicap? I always give first-timers 5 stones on 9x9 and it works just fine. Also, I can give them some immediate and easy-to-follow advice (just try to keep your stones connected), while for an even game I suppose they would just be totally lost as to how to start out. I recently watched a 25k teach someone go on KGS and she was going on about "Corners, Sides, Center" before even explaining the ko rule, let alone playing a game...
Sandy Harris I read something once that suggested giving a nine stone handicap on a 9 by 9 board at first. The writer was a dan player and said he sometimes lost to beginners that way, but they learned.
Karl Knechtel I've found that, incredible as it sounds, real beginners generally fail to make life with 5 stones on 9x9. Of course, it is really my fault for *only* teaching the actual *rules* before we start ;) I guess it's the same as playing Idiotbot, which in effect only makes life by accident. A beginning student might get the idea independantly that the liberty count matters before it reaches 1 or 0, but expecting them to appreciate eyes is hopeless - by the time they see the effect they have on White's stones, it's too late to make any of their own ;)
(Maybe I need to emphasize the territory concept more in explaining the scoring? But students never seem to pay attention to this. Atari go as a teaching method is in my mind completely unnecessary, because it seems that many people will seize on the idea of capturing rather than that of territory, no matter WHAT you say or do :D )
Anyway, the other way - trying to explain life and death as if it were in the "core rules" - leads down a slippery slope of overexplaining everything.
As for the whole corner/side/center thing, and everything being corner play on 9x9 - I've found that a poor explanation of the principle at the beginning can be very damaging to a student. I'll only talk about this stuff *at all* if the student explicitly asks about it, or if s/he has a tendency towards premature first and second line moves.