This is a good question; it's something I've been working on with my personal blog, and though I am not where I want to be just yet, I do have some advice based on what I've read and experienced.
First, I think that building relationships with other bloggers is important. The more you put yourself out there and comment on other blogs that are similar to yours, the more traffic you will get. Usually, the bloggers you follow will follow in kind, and you will develop some sort of relationship.
Next, you should make an effort to reply to your comments. This helps to foster those relationships and to show that you are interested in what your readers have to say.
You should have relevant tags that will guide readers towards your posts. It doesn't hurt to include share buttons for Facebook, Twitter, Reddit, etc., so readers have the opportunity to share your work with their friends. I made a Facebook page and a Twitter account for my blog, and though I haven't seen the traffic rise in these areas as much as I'd like, I keep it up because I think it's important to promote my blog as much as possible. It's also important to post consistently and often so that you don't have tumbleweeds traipsing along your site. I find myself giving up on blogs when they're not updated on a regular basis.
Good, clean writing that is error free and well produced is also crucial. Spelling and grammar errors are a turn off as are confusing, rambling posts about too many unrelated topics. Obviously, the content matter on which you focus is going to have an affect on readership as well. I write about pretty benign topics, and I think this affects traffic to my blog. In my experience, posts about celebrities get huge traffic. I wrote two posts that just mentioned James Franco, and I've gotten countless hits because of it. Apparently, he's quite the hot topic!
I am not sure if I've been a great help to you, but these are the areas on which I've been working, and I thought they might be somewhat useful to you, too. I recently queried several agents with a nonfiction manuscript, and the feedback I've gotten is "build your portfolio"! So, that is what I'm attempting to do, amongst other things.