What it means to be a sensei
I should begin by confessing an ignorance about Japanese custom. There may very well be a way of becoming a sensei, but for the sake of my comments, I will equate the term with the English word teacher.
As an English teacher myself, I've come to recognize that people with certificates are not the only teachers, and teaching in the classroom is not the only place I can offer my skills. All of this is to say that we can all teach each other something. Moreover, it could be said that older (or at least more experienced) individuals have a duty to teach the young (less experienced).
Hopefully the connections to Go are obvious. If I feel that my skills are considerably more advanced than those of my opponent (something I've only just now begun to experience -- it's quite a thrill), I offer to comment and teach. I don't pretend to have much help to offer, but I can point out a thing or two from time to time.
I just wish more of my advanced opponents would do the same. I'm very lucky to have this online resource (especially Holigor -- thanks be unto him for TeachingGame44), as well as a handful of folks I meet once in a while on IGS. But very often, I have my head handed to me by an advanced opponent, and s/he doesn't say two words of advice about what I should study in my playing. To me, this is the equivalent of my reading a student's essay, slashing through a couple of paragraphs, and giving him an F.
Because Go is such a wonderful game -- but also because it can be so frustrating, and a little encouragement can do so much to keep a person playing -- I feel that advanced players have a serious responsibility to keep the young blood flowing.
I guess IGS is simply not the place to find such kind of opponents. On KGS, players and observers can extremeley easily review a game when it's finished, and they very often do. The atmosphere is a thousand times nicer there, and the software client has been purposedly designed for teaching. Many strong players use now the facilities of this server to give private (and sometimes public) lessons. You might want to take a look...
Is this lack of feedback from your opponents just that they (passively) do not advance any advice or that they actively refuse to give any advice?
Some cultures hold it as disrespectful to give advice unless asked to do so. Some cultures give too much advice even when it is not asked for.
In my experience, stronger players have (almost) always been happy to give some advice, although sometimes I have had to ask for it. But I suppose that you can distinguish between a 'sensei' and a 'stronger player' by the willingness by which they offer their advice :^)
Something else which I think a sensei needs is humbleness. But wait, that is something every Go player should have :-)
Bill Spight: French saying: "Giving advice is like kissing: it costs nothing and is a pleasant thing to do." :-)
Dieter: ... which is why people often get harassed with good advice.
Stefan: Flemish saying: "Advice is the only thing that people like giving more than they like receiving."
HolIgor: IGS is a place where people come for a serious fight and not for a chat or teaching. IGS does not even have means for a post-mortem analysis. Moreover, most people there don't speak English, so no wonder that they don't speak to you during the game.
Now, they are strong. The medium rank on IGS is 2k, which means that the real-world kyu players constitute less than a half of people there. And these strong silent aliens came there for a war.
KGS is much nicer place and I would recommend to beginners playing there where people can speak English, are friendly and like to share their knowledge. I don't play there regularly but visit from time to time.
Scartol: I always say to stronger players: "Please feel free to comment as we play." I just checked out the KGS server, and it does look promising. Thanks for the advice.
BlueWyvern: I just thought I'd point out that IGS does in fact have a tool for postgame analysis, although it can be a bit of a pain. First you have to type "sgf <playername>" to get a listing of sgf files the server has stored. Then you type "teach <filename>" and you get a window with the game in it. You can either play variations or step through it with ">" or "<". On several occasions I have done a review with people, when they observe such a game, you can see all kibitzes. The downside is you can't cede control of the game like you can on KGS.
moonprince: I agree with the notion that more skilled players have an obligation to teach less skilled players, but teaching is a lot of work also. It isn't reasonable to expect teachers to teach everyone every time every game.
When I am playing with somebody who makes mistakes that I can recognize (as a novice myself, this is not often), I suggest to the player "We can review afterwards if you would like." Usually they agree, but sometimes they have obligations and must leave. Likewise, if you are particularly looking for a teaching game, it seems reasonable to ask up front if anyone is available for such. I too find KGS to be much friendlier for learning than other places I've tried as well.
I don't know the particulars of asking to become a student in go, but in other Japanese arts it's customary for the student to make a gift when he asks the sensei for lessons. Having an intermediary who is able to vouch for the student helps. Also, if a sensei has become aware of a promising student they may keep on eye them for a while, and then if they pan out, make them an offer. This does not seem to apply to an Internet environment though.
Tamsin: My theory is that teaching is good for you because it reinforces the simple but important stuff in your mind - by teaching the fundamentals, you are revising the fundamentals. Now, I find over and over, that as you get better at anything, you forget the simple things or emphasise them less, and rely on more advanced skills to maintain your level, with the result that you begin to slow down in your improvement - to "tread water". But it's the fundamentals that make the most difference, and if you can combine learning advanced skills with having the fundamentals constantly in mind, then you should be able to advance rapidly by exploiting the simple mistakes of those who are treading water. That's why, I believe, teaching is so very good for you.