STEPS

1.Register for a Google Adsense account, (Duh). Go to https://www.google.com/adsense/. After you registered, it's time to play the waiting game. Google takes approx. 2 - 3 days to check your website, and see that it's got the right content, etc, etc... Here's a note, Google tends to not let Blog sites to participate in the Google Adsense Program, you'll understand why, later on.  

2. Hopefully, you will now have a verified Google Adsense account. And you can log onto your Publisher's account.

3. Now, the money making begins, first of all, make sure that your site actually has VISITORS! If not, try to visit a traffic exchange site, or convince your siblings to visit it often. Customize your codes, and paste it onto your site.

For more information

http://www.google.com/adsense