When I taught creative writing for the first time, last year, I didn't teach dialogue. I claimed to have run out of time, and more or less had, but in truth I didn't shift the schedule to accomdate dialogue because I had no idea how to teach it.
I think it's inappropriate to relay compliments about myself, but a number of people have told me I write dialogue well, and most of the time I believe them. It seems logical that I would be good at it, since I love it! Definitely I've found that the things I find fun are also the things I can do well, but I've also find that people who are good at things can't teach them. Did you ever have your math-brained friend try to tutor you in algebra? It's horrible, right? Because they keeps saying like, "ok, and obviously the vector would go this way," and they actually have no way of explaining it if its not obvious to you. Mathy people's brains make too many math leaps and they can't retrace their steps for someone whose own brain doesn't leap.
What you want is a teacher who struggled and struggled and struggled with something, and eventually achieved some (possibly low) level of mastery. That person remembers every step of the process and is able to explain it clearly to the novice--a teacher that remembers what it is like to learn. Which is why I think my most useful lessons are on plot structure or self-editing or things of that nature--I struggle with those still, and my memories of my learning process are as recent as last night, so I can bring the kids some very well-rehearsed tips.
I am not saying I've "got" dialogue or am not constantly trying to improve--certainly I am, and there's plenty of room to do so. But dialogue is the fun part for me and I do bounce along more easily with that stuff than anything. And it's really hard to say why or how!
But for my students, I'll try. Start with the thing that every creative writing teacher--and anyone who has even heard of the process of creative writing--would advise is that if you want to write dialogue, listen to people talking. Absolutely! And not just your friends--listen to as wide a range as possible. Eavesdrop in restaurants and on transit. Make note of how people use certain words and how they vary--dresser or bureau? Snow machine or skidoo? "Bay-gal" or "bag-el"?
Of course, the flip side of this is that really good, really readable fictional speech is highly stylized, and if you use real speech to convey character you would need the length 0f an evening (a whole first date!) to catch an even slightly accurate portrait. I don't take notes and don't record--indeed, I never quote directly from strangers. When I listen, I just want to get the rhythms of their speech, turns of phrase, that sort of thing.
What to leave out? Sneezes, burps, apologies for dropping things on the floor, long descriptions of what a mutual friend is up to, repititions, speakers losing their place in the story for no reason, giving of directions, self-absorbed monologuing (unless it both a. reveals a lot of character and b. is funny), conversations about the weather that are actually about the weather, way-too-plot-heavy-garbage (some people probably actually say, "I don't think you love me anymore, Bruno. I think you have played me false" but they do not need to be immortalized in fiction).
In short: dialogue in realist fiction is *like* real speech, but *better*. So I brought hyper hyper stylist stuff--Pirandello, Beckett, Abbott and Costello. Oh, and it was funny stuff, too, at least in my opinion. I'm finding that the students feel the weight of "writing a story" really a lot--I wanted to remind them there's supposed to be some entertainment value here.
And then I taught them how to punctuation dialogue and then...well, it was a short day so then we were out of time, but that was pretty much all I had anyway. How *do* you teach dialogue?