When you are writing a blog, keeping a balance between writing what you want to write and what your readers want to read is a fine art.  With the help of keyword research tools, you can gain valuable insights into just what you should write about. 

In addition, keyword research can help you choose the most searched for phrase to match your topic.  For example, "freelance writing" may be more popular to searchers than "professional writing".  Finding the keywords people are actually using to search will help you in your quest to provide relevant, valuable content while attracting new readers.

The Google Adwords Keyword Tool is a free tool that you can use to learn how many searches are performed on a keyword phrase in a month, as well as how much advertisers are paying to advertise those keywords.  If you monetize your blog with Adsense, this can be a huge help in finding profitable words.

While your main goal should be to provide valuable information to your readers, there is no reason you cannot also choose keywords that will provide a little income for you as well.  After all, the research and time spent writing should be worth at least a little revenue.

So give the Keyword Tool a try, and enter your blog's main theme as a keyword search to see related keywords that might give you ideas for new posts.  Be careful not to get too sucked in to keyword research.  It is very easy to spend all your time researching and little time writing (don't ask me how I know this).