First, you must have good knowledge of the things you are writing about. After that you have to post interesting content regularly. IT is also important to spend some time and increase the popularity of your blog. I think that it is also a good idea to use some widgets that allow visitor interaction, because that way you will allow your readers to contribute to your blog. Another thing that you can do is to allow guest posts, because that is one of the sure ways to get better rankings in Google.
Those are just the main things, because there are many small details that you should take care of. However, I think that once you manage to keep up with them, you will become a successful blogger for sure.