Things which we MUST take note of before placing Ads from Google Adsense

Your Page requirements :
No Google ad may be placed on any non-content-based pages.

No Google ad or Google search box may be displayed on any domain parking websites, pop-ups, pop-unders, or in any email.

No Google ad may be placed on pages published specifically for the purpose of showing ads, whether or not the page content is relevant.

Elements on a page must not obscure any portion of the ads, and the ad colors must be such that any ad elements, including text and URL, are visible.
Clicks on Google ads must not result in a new browser window being launched.

Client Software :
A site or third party cannot display Google ads, search box, search results, or referral buttons as a result of the actions of any software application such as a toolbar.
No Google ad, search box, or referral code may be pasted into any software application.

Web pages displaying our ads, search box, search results, or referral buttons may not be loaded by any software that can trigger pop-ups, redirect users to unwanted websites, modify browser settings, or otherwise interfere with site navigation.
It is your responsibility to ensure that no ad network or affiliate uses such methods to direct traffic to pages that contain your AdSense code. Accounts involved in this type of activity may be permanently disabled.

Code Modification :
Any AdSense ad code, search box code, or referral code must be pasted directly into Web pages without modification. AdSense participants are not allowed to alter any portion of the ad code or change the layout, behavior, targeting, or delivery of ads for any reason.

Competitive Ads :
Google does not permit Google ads or search boxes accessing Google search services to be published on web pages that also contain what could be considered competing ads or services. If you have elected to receive contextually-targeted Google ads, this would include all other contextually-targeted ads or links on the same page as Google ads.
This would also include ads throughout the site that mimic Google ads or otherwise appear to be associated with Google on your site.
Although you may sell ads directly on your site, it is your responsibility to ensure these ads do not mimic Google ads. If you have elected to receive Google search services, this would include other search services on the same site and non-Google query-targeted ads. Google does allow affiliate or limited-text links.

Copyrighted material :
In order to avoid associations with copyright claims, website publishers may not display Google ads on web pages with MP3, Video, News Groups, and Image Results.

Incentives :
Web pages may not include incentives of any kind for users to click on ads. This includes encouraging users to click on the ads or to visit the advertisers' sites as well as drawing any undue attention to the ads. For example, your site cannot contain phrases such as "click here," "support us," "visit these links," or other similar language that could apply to any ad, regardless of content. These activities are strictly prohibited in order to avoid potential inflation of advertiser costs. In addition, publishers may not bring unnatural attention to sites displaying ads or referral buttons through unsolicited mass emails or unwanted advertisements on third-party websites. Publishers are also not permitted to use deceptive or unnatural means to draw attention to or incite clicks on referral buttons.

Labeling Ads :
Publishers may not label the ads with text other than "sponsored links" or "advertisements." This includes any text directly above our ads that could be confused with, or attempt to be associated with Google ads.

Language :
Adsense Ads should not be placed in unsupported languages.

Prohibited Clicks and Impressions :
Any method that artificially generates clicks or impressions is strictly prohibited. These prohibited methods include but are not limited to: repeated manual clicks or impressions, incentives to click or to generate impressions, using robots, automated click and impression generating tools, third-party services that generate clicks or impressions such as paid-to-click, paid-to-surf, autosurf, and click-exchange programs, or any deceptive software. Please note that clicking on your own ads for any reason is prohibited, to avoid potential inflation of advertiser costs.

Note : These are just some most common rules which we fail toread and concentrate on.
Click Here for detailed report of Adsense terms and conditions.