1.You need to sign up for an Adsense account. It's a simple process, but you will have a short wait while your site is approved. Once your website is approved you are free to use Adsense ads on any site you have, but just because you don't need to have the other sites approved you will still need to make sure you are following the Adsense terms. They are very strict and if you are caught breaking their terms you stand the risk of having your account suspended.

2. Building your pages will be your next step. The key to this is finding a keyword that has a lot of demand, but not a lot of competition. If you want to go the free route you can use nichebot to find the demand and the competion. If you have the money you will get a much better selection of keywords with Wordtracker. You want to use the keyword in the title of your page and in the body of the page a few times. For content you can write your own or you can visit an article directory and find a good article to use on your page, if you do that look for an article that has your keyword in the body a few times. If you do use someone elses article be sure there bio is included on your site, that is the reason they allow you to use their article. 3. We are ready to add the Adsense ads to the site now. You are allowed to use three ads, A good placement of the ads should be one at the top of the page, one vertical ad on the right side, and one ad at the bottom. If you decide to use just one ad I would put it at the top of the page. The Asense ads will have a border around them, but most people remove that by changing the color of the border the same color of the page, so if your page is white just change the border color white and you won't see the border. You want the ad to blend in to your page as much as possible.

Ok, now it's just a matter of just waiting for traffic and you can start getting paid each time someone clicks on the Adsense ads. It may take awhile to get your pages indexed, so in the mean time you might need to write a few articles to get a little traffic to your site. There are other ways to build sites, some people use programs that will build thousands of pages quickly, but I think the search engines have been able to identify most of those types of sites so I don't recommend using them. If you are looking for a faster way to get sites up I would recommend buying some of the ready made Adsense sites, Most of them are well built with all the bells and whistles and not very expensive.