Not long after I started grad school, one of my professors suggested Taking the Leap by Cay Lang.
It had a lot of great "how to" information in it - how to approach galleries, organize a show, write a press release, photograph your work, etc.
The thing that I remember most about it, though, was that the author encouraged artists not to compromise. She says that you shouldn't try to find a style or subject matter that will "sell" but that you should create your artwork according to your own vision and then put it out there. Someone will like it. Eventually.
So that's the approach that I've embraced, for good or bad. Art is so subjective. Everybody responds differently, which is what makes it so exciting. So I think that if I put my stuff out there as much as I can, eventually I'll find enough people that like it.
Not that you shouldn't grow and change. Feedback is crucial. You'll get an idea of what people respond to and then you can build on that, incorporating new ideas into your work to keep it fresh.
I see artists that find something that works and it seems like they cling to it and never grow or change or do anything else. Like I'm one to talk - I've been doing tornadoes for 5 years!