When I started off writing, I would often see articles and emails floating around saying how important it was to write to your market. Although I could understand the sense of this, in another way I could not see the point. I came to writing late, overwhelmed by an urge to develop my ideas and turn them into story. Frankly, if I could not develop my ideas my way, then I could not see the point of all of the pain to begin with. I had other ways to make money - and good money at that.
So I guess I did my own thing, the result of which is various manuscripts that were not judged commercial, or did not fit into the neat marketing categories. The most notorious of which is Warriors of the Blessed Realms, which is a hybrid SF/Urban Fantasy/Heroic Fantasy that straddles various worlds from contemporary Earth to the Vaults of Sheol and the Blessed Realms themselves.
Years ago (2003), an editor rang me to say they liked WBR, but perhaps could I take out the SF? Well, the SF was so integral to the story I could only answer - No. As a result, I missed a great opportunity for a potential sale. Basically removing the SF would have resulted in a novel that had very little in common (at least on a conceptual level) with the original concept. (I think I was actually in shock at the question, which probably dulled my wits a little.)
What I have realised since then is I should have said - YES!! - then proceeded to write a completely new novel with the same title and characters:) I am still kicking myself after all this time.
While I don't think I would ever really 'chase' a market, I have learned since then that I can generate ideas out of just about any context imaginable, so if someone gives me a solid reason to do it (i.e. they will publish it) then I can make use of any material to weave a story.
Right - now I have blurted out my biggest publishing blunder. . .
I have known quite a few writers who have deliberately set out to capitalize on trends. I'm not sure this has really worked out all that well for them. The reason is that by the time something is recognised as 'in' the trend is really quite well established. Writing a good novel takes time. If you add the fact that the new movement/innovation/setting has probably really been around for at least a decade by the time LOCUS does a special on it, then add the five years it takes to really produce a masterpiece - that's 15 years. Time enough for the next new thing to come along.
I've seen a lot of writers run foul of this timeline. Their novels get shunted aside in the tide of copycats that flood onto the editor's desk.
Now - anticipating a trend is something different. Can anyone actually do it? I'm not sure. But some people have sure as Hell got lucky!
I think this is one of the reasons that great writers are often not recognised in their lifetime. Perhaps they are ahead of there time, perhaps they are writing something that is seen as having had its day. Maybe it takes fifty years before the cycle comes around again and someone actually picks their novel up and assesses it on its merits and realises its brilliance.
So do you try to anticipate or follow current trends? Or do you just follow your crazy ideas wherever they lead?