One of the great things about being a professional academic is that you get to write about whatever you want. One of the hard things about being a professional academic is figuring out what to write about and what not to write about. I'm curious to know how others approach this issue, but I'll begin with my own account as a cautionary tale.
Things were easier for me in graduate school. Once I'd chosen a dissertation topic, the next few years seemed pretty well mapped out. I'd spend a few years writing my dissertation, after which I'd spend a few more spinning papers out of the major chapters and building a research program on those first few papers. At first, things went according to plan. The dissertation came along at a nice clip, and one of the early chapters was accepted by a journal before I'd defended the dissertation. The paper containing my "main ideas," however, has languished at one journal or another for the past three years. Because it's somewhat idiosyncratic and has received mixed responses, I'm not sure about building a research program on it until it's published. I've presented versions of that paper at conferences and have made some progress on it. However, I'm lucky enough to be on the tenure clock now, and so I can't afford to twiddle my thumbs while journal referees twiddle theirs.
Without the direction established by my dissertation, I've taken what I'll call an "opportunistic approach" to writing. I have quite varied philosophical interests, and I've been indulging them whenever an opportunity presents itself to write a potentially publishable piece about one of those interests (e.g., a conference CFP, an interesting paper comes out about which I have something to say, an invitation to contribute to a volume, etc.). I suppose my strategy has been to try to grab some low-hanging fruit while trying to publish my "primary" research.
In short, this strategy hasn't worked very well. I've produced a bunch of (mostly unpublished) papers on a bunch of different topics. Aside from one coherent research program that's emerged from an opportunistic interdisciplinary collaboration with a friend, most of these papers are mediocre at best. There are two or three that might pan out, but I wouldn't be that surprised if they don't. I think I'm just not deeply entrenched enough in the relevant literatures to execute these papers well. What's more, many of the papers are on topics around which I don't really want to build a research program. If I can get them published, they'll be "one off" pieces. So, I don't have much incentive to get deep enough into the relevant literature to make the paper work.
What strategies have worked for people in identifying publishable ideas and/or fruitful research programs? What strategies haven't been working?