Have the Right Amount of Content

At the same time, don’t put too little on a page. Having one
paragraph on a page makes it look like your site has nothing
to offer, and the customer has little to gain by venturing to
other pages. Address the topic of the page and cover it well.
It’s crucial to successful ad revenue to organize your pages
well. If you have ads ¾ of the way down the page, but
you’ve bored the customer before he got halfway down the
page, then you’ve lost ad revenue. For the same reason, if
you don’t have enough information and the customer
doesn’t click through to other pages where there are ads,
again, you’ve lost revenue.
Think of your website as a book. There always has to be
enough to make them turn the page, but not so much that
they know how the story ends after reading the first
paragraph.
This site below doesn’t have enough content on the page to
support Google AdSense. Half the page is blank. The
solution here would be to move the ads up into the content
or move them to another page. To a visitor, the site looks
like it’s missing something it needs. Besides that, the ads
really stand out as just that: ads.

Free Content for Websites
There are sites that will provide you with free content for
your site, including articles, polls, quizzes, etc. You can use
those that relate to your site’s content in exchange for a link
back. Articles and quizzes can draw more visitors to your
site, but remember the content must be quality. If you wrap
up a big box for a Christmas present for someone, but fill
the box with garbage, they’re not going to be impressed.
It’s the same way with content.
Remember that the more quality content you have, the
more your visitors are going to trust that the ads you display
are quality, as well. And the more interesting content you
have, the more keywords you’ll use. It’ll make your site
more prominent in the search engines. All this translates to
more visitors and a higher CTR with AdSense.
http://www.freshcontent.net and http://www.pollhead.com
are two of many sites that offer free content to Webmasters.