Google Adsense
If you don't already know, Google Adsense is a program created by Google. You can sign up for Adsense and display Google ads on your website(s) or blog(s). Every time someone clicks on an ad, you get paid! Prices differ between companies.
You Need A Website Or Blog
The first thing you need to sign up for Google Adsense is a website or a blog. A good website to you if you don't want to pay anything for your site is www.blogger.com. You can make a free blog on blogger and use this to post your adsense ads.
You can make a website and purchase a web address if you choose, but you do not have to.
Make It Pretty
Now that you have a blog or a website you want it to look good. Add pictures, videos, and text. Make sure that everything on your page relates to your topic(s). Google will review your page before approving it for Adsense so you want it to look professional.
Get Traffic
Once your page is ready to show, start advertising it! Google will base their decision on your traffic level as well as your page's appearance. The more traffic you have visiting your page the greater your chances of being approved.
A good way to get traffic is to post links to your page on forums, threads, and more.
Also be sure to tell all of your friends. Have a myspace? Myspace is great for FREE advertising! Post links on you myspace page and in comments and messages to your friends.
All traffic is good traffic so advertise everywhere!
Now You're Ready
So now you have a pretty, informative, popular webpage and you are ready to submit it to Google Adsense. Once you are confident in your page go to www.google.com/adsense and submit it. You will receive a reply in a timely manner, hopefully you get approved then you will be ready to make some extra money! Don't worry if you do not get approved you can fix up your page and resubmit it later.