I remember asking an expert years ago the question "How can a blog get lots of traffic?"

He answered: "Make a posting to it every day, make sure each posting is on the same subject, and that the content is valuable to the visitor. After a year of that dedication, you might notice traffic picking up."

When you make an entry in your Fishing blog about Knitting, you fail to reinforce your position for relevant content for Fishing. It's like selling a knitting kit in a fishing tackle store. You waste space, confuse visitors and offer little value. Just like physical stores, people won't come to your fishing blog to read about knitting. In fact, for those who do come to read about fishing, an off-subject blog entry is an invitation to depart.

Bloggers get distracted. They start off their exciting new blog with some great material on their subject and before you know it, they're talking about their vacation in Scotland and how they cured their Athlete's Foot using lemon juice.

Subject matter density increases your chances of getting displayed early in search results. Stick to your subject, post every day and stay with topics that visitors are interested in today.

For example, if your blog is a political pundit site, when the Presidential Primaries are on, talk about them. When the presidential election is on, talk about that.