Like Henry, I get a lot of emails from young/new bloggers asking for advice. I will now point them to this wonderfully succinct summary on TrueHoop, which covers the big points, but I'll sum it up:
Find something that you care about and put in a ton of effort covering it in a way that no one else does, serving the community that would care the most.
That's a pretty malleable statement: It could mean you're the only one covering a specific niche (good); it could mean you're the best at covering a more competitive niche (great for you, but very very difficult); it definitely means that effort counts, regardless; it definitely means that more focus is better; it definitely means that you should worry less about getting that "big" page-view hit from Deadspin and more about your core audience; it means that the next "big" things in sports blogging will assuredly involve some form of innovation.
This is one of my favorite topics in the world, and I could go on about it for a while, but I'll spare you and leave it there for now.