Copied from my Blog. I thought it might be useful to someone here as well.
I shouldn't be ignoring the forum in favor of My journal anyway.

I’m on vacation from work, so I had plenty of time for a field trip. My excursion was to the bookstore where I did some market research. There were several things that I was looking for… things that any aspiring writer should pay attention to. Through understanding the market, you will find yourself better able to meet the current needs of your readers and possible improve your chances for publication. Here are a few of the things I made note of during my journey up and down the aisles:

1. What is the average length of fiction in your chosen genre?
2. Which publishers have the bestsellers lately?
3. Which publishers have the most books on the shelves?
4. What types of stories are currently popular?
5. Do the bestsellers have male or female protagonist? (This is an alternating reader preference where the trend changes every few years)
6. What are the recent POV trends? First person? Third?
7. Are there any good agents mentioned on the author’s acknowledgments pages?
8. Look at the opening pages: Do they ease into the story? Or, dive into the action?
9. Types of titles: I noticed that single-word titles are making a comeback. (Good news for me!)
10. Series? Or stand-alone fiction? There seems to be a cyclical pattern of preference here, and it looks like we’re again entering the “Series” wave.

All of these things are areas of information that should not be ignored by the prospective debut novelist. There will be time to forge your own path later when you are on the bestseller list. For now, it would serve you best to produce exactly what the market is looking for.

Identifying the current trends is important. I was happy to find that the trends that I identified a year ago (and tailored my novel after) are still the apparent trends of today.

Also, on a side note, I find it encouraging to read through a few pages of the books that are on those hallowed shelves. There is so much out there that is “weak” material. I may be a little arrogant for saying so, but I’m certain that my material is better than at least some of the novels in print. That always makes me feel hopeful. Sometimes it’s a good feeling to say, “Hey, my stuff is better than that stuff!”

And no, I don’t think it’s my imagination. You’ve all seen what’s on the shelves. Scary.

One thing worth keeping in mind - there's a lag time. Aside from the time it takes to write a novel and get it accepted, there's time for editing, proofreading, printing, and distribution. If the trends are fairly stable, that's all fine, but if you see the trend start to change, your book may not be out in time to even catch the tail end of that.

However, be wary of focusing too much on trends, or you'll get a shitty novel that's just like every other. Consider "urban fantasy": there were a few hits, and then Laura K Hamilton's Anita Blake series went big, and now there's about 80 knock-offs with a plucky female crime-fighting witch battling vampires and such.

Mokele

But by looking at what's out there, you can get an idea of not just where the market IS, but also where the market is HEADING

As long as you know the direction, you can increase your chances of scoring a hit. Shoot in front of the duck.

It's still better than entering the game blind.