Signing up for Google adsense is free. After signing up, login to your adsense account to get their codes and insert them to your webpage(s).

Here are some rules you have to follow to make money from Google and not getting banned from taking part in the adsense program:

• You are allowed 1 link unit, 1 referral button per product, 2 search boxes and 3 ad units per page

• Do not alter adsense codes. The generated codes must be pasted to your webpage exactly as they are, as changing the codes can cause errors on your webpage and is against the adsense program policies

• Do not click your own adsense ads, not even to test them

• Do not ask or encourage anyone to click your ads

• Do not have adsense ads in emails or thank-you webpage

• Do not advertise your website in auto-surf, pay-to-surf, pay-to-read or pay-to-click services as these will cause invalid clicks. Robots or click exchanges are also not allowed

• Do not display adsense ads in gambling, porn or illegal sites

• Do not display adsense ads in sites containing video, MP3, newsgroups and image results due to copyright reasons

• Do not display adsense ads in sites with pop-ups or automatic software installs

• Ensure your webpage is never loaded inside an unrequested popup

• Do not display other contextual ads on the same page as adsense ads. For example, your site could rotate between displaying Yahoo or Google adsense ads on each page, but NOT adsense and Yahoo ads on the same page

• Your webpage language must be one of the supported languages

• Do not check your adsense account from a public computer, or from someone's computer. Google records your adsense login and will remember from which PC you are logged in, and if someone uses it to visit your site, and clicks your ads, Google may penalised you

Here are some useful tips which you may like to know to boost your adsense revenue:

• Ad placement is important. Certain locations tend to be more successful than others. For example, "above the fold" of the webpage, that is, before you you need to scroll down the page, and the upper left-hand corner of the page.
  
  Read google "Optimization Tips" in the AdSense Help Center as it will help you to decide where to position your ads and which ad formats you should use. See Optimization Tips for details.

• Unobtrusive ads can boost your revenue. Many publishers find that visitors are more likely to see and click on Google ads, when the ads themselves blend into the overall theme of the page. In this way the ads do not stand out as being advertisements

• Try to use text instead of graphics to display the name of the website, page title and headline

• Keywords

  • The more you use your keywords, the more likely you are going to get ads on those topics

  • Place keywords at the beginning of your content and repeat them. Repeating keywords makes it easier

    for adsense to figure out what your webpage is all about.
    
    However, do not overdo the keyword targeting as it may make your text look awkward to a reader and may also be considered as spam by search engines. Google may also give you worse ads as a result of it

  • The title of the page should contain the keyword

  • Keyword should appear in at least one h1 tag

  • Keyword should appear in bold (b) and at least once

  • Google adsense spider, crawler or indexer searches your content for keywords and then displays ads for those keywords, ie., contextually targeted ads

  • You can earn more by writing topics related to high paying ads like mesothelioma, life insurance, loans, mortgages, real estate, computers and lots more. You can search for good keywords using Top Paying Keywords

• If your site uses frame make sure your ads are placed inside the frame where your content is, otherwise adsense will not provide relevant ads for your content

• Use alternative ads when adsense cannot display ads on your webpage. When it cannot find a suitable ad for your webpage, adsense will display a "Public Service Ad". You do not make money from a "Public Service Ad". Adsense allows you to use an alternative ad like your affiliate program instead of the "Public Service Ad"