Google AdSense advertising is extremely common on any site with changing content -- especially blogs. Google's service is free to use, easy to implement, and provides advertising based on the keywords Google finds on your pages: Write a post about fried chicken, and you might get Google AdSense ads for cooking supplies and restaurants. And these ads are contextual on a page-by-page basis, so every permalink page on your blog has its own set of topic-appropriate ads.

Each time a reader clicks a link in one of these ads, you earn money. You choose where the ads are on your pages, what they look like, and even what kinds of advertisers to display. You can see Google AdSense ads on the Apartment Therapy blog.

You can also include a Google search box on your blog. Users who use the search box from your blog get targeted Google ads in their search results -- and you receive money from any ads they click.

You can sign up for Google AdSense by opening a Web browser and following the steps at Google's AdSense sign up page.

After you finish the application, Google reviews your blog, and if it approves your application, you have to provide some additional information: Social Security number, Employer Identification Number, and so on. The review Google conducts ensures that the Web site the ads are placed on meets Google's editorial guidelines (for example, no obscenity).

After Google completes its review, you receive instructions on how to customize and place the ads into your blog templates. You may need a little help from your technical staff or some HTML skills of your own.

The ads appear automatically on your pages based on the content of your blog after you add the code to your templates. Visit the Google AdSense site to customize the look of your ads, check your earnings, and remove certain advertisers (such as your competitors!) from the ads that appear on your site.