Content is the king - In the blogging world so diverse and big, you need to establish yourself with a distinction. the only road to it is good, original and valuable content. Be creative, different and surprise your readers once in a while.
Put advertisement but make sure that your blog visitor doesn't get irritated when ads pop up one after another like a flood.
Blog for the fun of it and show character. It is immaterial how many write about a particular subject, it is how you write the matters.