Look for what interests you. Don't worry about whether it's been done before (its ALL been done before) and just do what you want, work out ideas, explore. When you find something that draws your eye try to figure out why it did so and present that to the viewer. Look at the work of others (all sorts of stuff, not just what you like at first glance), set aside the images that you liked and then look for something similar to work with. Use the idea of what you liked in their work with your own subjects.
It's not always easy breaking out of a rut, and I can only really speak from my own experience, but when I first started photographing I tried to make my pictures look like what I though people liked. Only after I dropped that line of thought and just let myself explore my own ideas did I begin to really do something I liked. I took the time to find what I liked in my pictures and thought about why I liked that aspect. I tried applying that same idea to other things. It also helped me much later in life to talk to people who were not into photography - people who painted and worked in mixed media specifically, but anyone should do - about what inspired them. This opened my eyes to a whole new world of possibilities, and it allowed me to see my own work in a whole new light. I was able to do quite a bit more after than than I even could before...
- Randy