(It becomes less and less of a rant every day, I think).
This could also be a guide for making fantasy humorous, as well. I hope. I love reading fantasy that makes fun of clichés, and whatever gods you believe in know there should be more of it.
1) Never make fun of the magic. If the fantasy turns against its own base, then it becomes a cheat, on par with saying "This is a dream!" at the end of a long and complicated story. It's a way of making the fantasy not matter. Parody fantasy has to walk a thin line, I think, between laughing at the genre it parodies and bitter mockery. Otherwise, it begins to seem as if the author hates the genre and is mocking fantasy itself, rather than the bad things about that particular genre.
This does not mean that you can't make fun of various aspects of the cliches. I have a lot of fun poking at elemental magic, earth goddesses, elven magic, and so on. But I have read a few books where the magic was explained away at the end as delusion, making me sick to my stomach. If you want to write a book that doesn't use magic, why waste your time attacking fantasy? There are plenty of other books out there that don't use magic, and that you could probably have more fun writing.
2) Pursue the logical consequences. One of the biggest faults of generic fantasy, no matter what clichés it tends towards, is that it ignores what would happen in "reality" because of those clichés. The king starts to rule over a land blasted by famine and war, but somehow the harvest is still rolling in regularly in the fall, and he never has to buy crops from other lands. The princess has spent most of the book crying and fainting, but somehow everyone accepts her as a strong queen. Two people have spent the first two books of the trilogy hating each other, but somehow fall in love in the third.
A great, and very easy, way of writing parody fantasy is to show those logical consequences, stir a little reality into the fantasy. The over-confident king has to deal with the failure of the harvest. The nobles promptly start plotting to overthrow the whiny, weepy queen, and she spends so much time weeping and wailing that she never notices. The love affair doesn't end in happily ever after.
This requires a certain cynical turn of mind, and the willingness to create annoying characters, but it can provide endless hours of entertainment. Believe me, I know.
3) Use pompous declarations without the time necessary for suspension of disbelief. It is possible that, in a fantasy where a lot of pages have been devoted to the idea that everyone is noble and heroic and serious, that the sentence "A lion and his Spider have gone to rescue him" (to use an example from my own writing) would sound fine. It doesn't sound fine when it's just dropped in there casually, without buildup.
Similarly, a lot of the edicts, dramatic speeches, and pep talks that people in fantasy give are ridiculous when removed from their context. This doesn't mean that I encourage fantasy readers to read along with their minds intent on destroying the context instead of appreciating it.
4) Never build up too much suspension of disbelief. The traditional fantasy world is real and not-real; the audience knows these things can't happen on modern Earth, but is willing to pretend they can happen for a little while, if the author does a good enough job of giving them an alternate space in which the happenings occur. The parodic fantasy world has something a bit different to do.
The parodic fantasy world has to exist on three levels, technically: real, not-real, and would-be-real. This applies certainly to the abstraction of logical consequences from clichés that I mentioned above, but also to many other things. The parody fantasy world is not-real because it is fantasy, real in the sense that the audience is willing to accept it that way between the pages of a book, and would-be-real in the sense that it brings up what it needs of reality and places it between the pages. Almost all parody fantasy techniques that I can think of do this, whether they're abstracting consequences, mocking a specific other fantasy work, or referring to things in the real world (one of the many excellent ways that Terry Pratchett handles his Discworld series, by making it reflect issues such as affirmative action and real-world artifacts such as guns).
This can make writing parodic fantasy more complicated, but also wonderfully easy- particularly if one is relying on the tier of real-world references, and making the would-be-real blend with the real.
5) Connect the things you're laughing at to other things in the fantasy world. Mockery is even more fun when it doesn't stand in a vacuum. If you have a feisty, rebellious princess run away from home and get into trouble instead of miraculously succeeding at all she does, perhaps she can be captured by the bumbling pirates, or caught in the intrigues of the nobles who ineffectively use poisons and labyrinthine plotting when a simple assassination would be much more effective. A parody that hits just one note all the way, just one joke, is a tiresome parody. A constantly moving web of jokes is better, and if you can set them up in such a way that the happening of one joke triggers the next, it's even better.
There are no lack of things to parody in fantasy. The genre is vastly imitative, and while that's often a good thing (in that many plots and characters which would otherwise be clichés get a chance to shine), it's also often a bad thing (fantasy authors steal from each other without bothering to consider the consequences of writing "just one more" feisty-princess or royal-heir story). Even within just one plot, there's more than one joke to exploit.
6) Strike your audience at all levels. Thus, don't parody just in terms of plots, or silly things the characters say, or descriptive language, or purple prose, or logical consequences. Do everything at once.
This might entail multiple revisions of the material, depending on how you work. Perhaps you go through a scene paying attention to the language first (and parody does require more attention to that than most), and then go back and add in silly actions as well. Perhaps you have a day where you're really on the ball as far as adding a logical twist to the plot, but find out that you're still taking your main character far too seriously, and need to come back the next. Fantasy writing, like all writing, is capable of revision, and unless you've already gotten it published, nothing is set in stone.
7) Know your source material. The best parody is funny, I think, not only because it mocks its target, but because it could be its target, if just looked at from a different angle. The parodist should be good at writing clichéd plots, purple prose, silly love poetry, or whatever else she wants to attack. This forces the audience to reevaluate the source material twice, both in the course of laughing at it and in the course of laughing at the parody's excesses.
Probably the only way to know the source material that well is to read it. (Otherwise, the situation becomes that I mentioned in point one, where someone is mocking the genre out of bitterness and ignorance). It's not such a chore. Yes, there's lots of schlock out there, but a steady diet of schlock doesn't physically hurt you, and there are some real gems to be found in sifting through the pile. Besides, the more bad fantasy there is and the better you know how to make your parody stand out against it, the harder people will laugh.
Not nearly everything, but it's hard to do without giving more specific examples. Maybe tomorrow.