Welcome!
I agree with Sherif, definitely narrowing your niche is key. You've probably already heard of Darren Rowse. He makes six figures per year from his Photography blog. You may want to check out his blog just to get some ideas if you haven't already.
http://digital-photography-school.com/blog/
Of course I'm not suggesting that you copy his style or topic, but I learn a lot from studying other successful bloggers and webmasters by watching how they make use of Twitter, their writing style, how they communicate with their audience, etc.
Another thing to keep in mind as you're brainstorming is make sure you look at what's already been done. If you are thinking of doing a site for photography newbies, take a look at the sites that already exist on this topic. What are they missing that you can capitalize on? Is there one key component they always leave out that you could cover?
When you think along those lines, that's a good way to grab a nice piece of the market for your niche. Try to think outside the box and offer something unique or present your info in a way that hasn't really been done.
Hope that helps.