FIRST THINGS FIRST. Before you even begin to use Adsense as a monetization tool, make sure there are relevant ads for your site or pages. In most cases, you will have determined this long before you even embarked on site design or content development. However, if you are thinking of adding Adsense to an existing site built with other monetization strategies originally in mind, you may not have bothered checking to see if other advertisers were going after that particular market. Be sure you are addressing a topic for which ads exist in sufficient quantity. If related advertising is sparse, it will difficult to avoid irrelevant ads.
KEYWORDS MATTER. You do not want content that is overstuffed with particular keywords to point of destroying readability and value, but you do want to make sure your materials make liberal use of on-topic keywords likely to spawn the most relevant possible ads. Experts maintain that using keywords with your titles and H1 tags is an excellent way to assist in getting the most relevant possible ads. This has added advantages in terms of search engine optimization, as well.
METATAGS. Once upon a time, metatags were a critical aspect of search engine optimization in general. Although the engines rely upon metatags far less than they once did, there is some evidence to suggest that using ad-triggering keywords in your pages’ meta-tags may increase the relevance of the advertisements displayed. This strategy may help, and it certainly cannot hurt.
LOOK FOR LACKLUSTER CONTENT. Many sites to a great job of supplying content related to particular themes or keywords in the main portion of a page, but have sidebars, headers and footers filled with less targeted terms and material. Take a long look at your navigational elements and other "side of the page" text and remove keyword terminology that may be leading to irrelevant ad service. Alternatively, you can use Adsense’s section targeting tool to remove those areas from Adsense’s consideration completely, so long as you do not plan to display ad blocks or ad link units in those areas.
TIGHT THEMING. You want to keep content tightly themed. That means you do not want to feature long, rambling articles that cover multiple topics. Instead, rely upon materials that address singular issues. You also do not want to feature multiple chunks of content on disparate matters on the same page for that very same reason. The value of tight theming may extend past individual pages. Many publishers argue that Adsense tends to reward tightly-themed overall sites with more relevant ads, as well. Even though this aspect of theming is not as well researched and proven, it makes sense to follow the practice, because of the search engine optimization advantages of having a focused site.
BLOCK THE BAD ADS. Monitor your site regularly and take note when irrelevant ads appear. Then, take the time to add them to your blacklist for the site. Google does give you the ability to block individual ads via the Competitive Ad Filter. If you block out commonly served irrelevant ads, you may improve your chances of featuring more ads upon which your visitors will actually click.
The more contextually relevant the ads appearing on your site are, the more clicks you can expect to see. As such, it is important to make an effort to use a combination of proven SEO methods that also work well with Adsense and some program-specific maneuvers to secure the best possible ads on your site.