First, you need to do SEO (Search Engine Optimization). Get this book: Search Engine Optimization-An Hour a Day by Grapone and Couzin.
I use the Flexibility 2 1.0 for my Theme. It's free.
Next, you need to get backlinks. That is, you need to have a lot of Google high page rank websites pointing to your blog.
One way to get back links is to write articles and submit them to article directories like *************, **********, etc. Sprinkle your articles with keywords and link back to your blog using anchor text with HTML, e.g., <a href="http://www.yourblogname.com/">This is anchor text.</a>.
Next, you should have a bio or resource box at the bottom of your article that has links back to your blog. Just Google "resource box" for examples.
Next you need to create accounts with Social Network sites, Social Bookmaking sites, Video Sites, and RSS sites like Feedage.
Then you must connect your blog to all those sites.
The links given will hopefully answer this question. There are many tools to help you see where you stand and these will provide suggestions as what is to be done to improve your site for SEs. Might look through these: