Adsense-specific checklist of optimization points should be in mind before starting any site this will help not only with relevant ads on pages but also helps you get better ranking in search engines.

1. Have only one subject per page. Get your site fiercely organized, and eliminate extraneous content from any page. Don’t be afraid to add pages to accommodate short subjects that don’t fit on other pages. Let there be no question as to what a page is about. 
2. Determine key concepts, words, and phrases. For each page, that is. Then, make sure those words and phrases are represented on the page. Pay particular attention to getting those words into headlines. Your concentration of keywords should be skewed toward the top of the page. Don’t go overboard; your text must read naturally or your visitors (and Google) will know that you’re spamming them. 
3. Put keywords in your tags. Take those keywords and phrases from the preceding item and put them into your meta tags (the keyword, description, and title tags). Don’t use any word more than three times in any single tag. 
4. Use text instead of images. Google Crawler doesn’t understand words that are embedded in images, such as what you often seen in navigation buttons. If possible replace the buttons with text navigation links or put proper alt tags with all of your images.

Try to fulfill these points before opening an Adsense account. Ideally, your site is in its optimized state when Google first crawl it. You don’t know how often your site will be crawled in the future, so getting properly indexed the first time is the key.