There are two ways to think about AdSense: you can think of it as a way to use your website to make money; and you can think of it as a way to make money with a website.
What's the difference?
The difference is in the content. In the first case, you already have a website and you simply put AdSense on the page to turn it into cash. You might change the content a little to influence the ads and you could make sure that you include the best keywords to bring you the highest revenues. You should certainly play with the way the ads look on the page to make them attractive and unobtrusive - and there's a huge range of different strategies you can use to do that.
Ultimately though, the content is there already. You're just using AdSense to turn the content you're going to create anyway into money - and you're going to use AdSense secrets to make those revenues as high as possible.
But lots of people also want to build a website from scratch for the sole purpose of cashing in on all the money available through AdSense. There's nothing wrong with that - provided the content is high quality.
This is crucial. Google doesn't take kindly to sites packed with keywords and all sorts of other garbage just to provide a space to put up an AdSense unit. There's a good chance they won't approve the site, and little chance, even if they did, that you'd get any click-throughs.
But that doesn't mean you have to really bust a gut to create the sort of website that brings you a small fortune in AdSense revenues. In my book, Google AdSense Secrets, I discuss in detail a number of different methods that you can use to create great content quickly and easily. Some of these methods cost a little money; some are completely free and still give you outstanding content. Whichever method you use though the important to remember is that your site has to have real content that people will genuinely enjoy reading. There's no point in trying to cut corners in creating content - and absolutely no revenue to gain.
Reference: Joel Comm
Joel Comm is Dr. AdSense, an Internet entrepreneur who has been online for more than 20 years. Joel is co-creator of ClassicGames.com, now known as Yahoo! Games and is the author of the web's best-selling AdSense ebook, "Google AdSense Secrets (Or What Google Never Told You About Making Money With Adsense)".