From my personal experience and from speaking with many other publishers, it seems that many of them cannot even garner enough earnings to trigger off payment from Google (USD $100). This is really sad because much give up before even reaching the halfway mark. Imagine adding up all the quitters, the amount of advertising money Google would have pocketed without paying a cent!
Point #1 Find Your Niche.
You need to know about your topic or subject fully and be at least knowledgeable about it. You write quality content, you get quality ads shown. It is as simple as that. If you really found a profitable niche but know nuts about it, you can always use free articles (like this one) and post them on your site with their links on them of course. It is an easy and quick way to get quality content for your site.
Point #2 Laser Focused Theme.
You need to fully concentrate on your topic and area of interest. Do not deviate from it even a single bit! The reason behind this is to get the MOST relevant ads to your content which in turn will be the most likely to interest the visitor and get clicked on.
Point #3 Website Navigation.
Do not trick the visitor, do not confuse the visitor, do not attempt to hide the ad but do not blast the ad at the same time. Create your navigation in such a way that your ads appear unobtrusive and yet viewable. It is advisable to put more than one ad but does not cramp your page with ads, it turns the visitor off.
Point #4 Key Word Density
Although Google doesn’t release exact details as to how they determine the ads to serve on a given page. We do know the content (and words) of the page that matters. Before serving ads on a page, then, you might want to check its keyword density to see what words pop up most frequently.
Point #5 Maintain Content Readability
Advertisements should not distract from your content, or else your visitors will be driven away. Make AdSense a cohesive part of your site design, not something slapped in at the last minute or some hastily put up page.
Point #6 Ask Them!
Point #7 Do Nots.
Do not click on your own ads neither should you ask others to click on your Google Ads. Do not manually change or modify your ad code. Do not place Google Ads on sites that include prohibited/questionable content (e.g.: adult sites, hate sites) Do not employ cloaking, hidden text, or farm links. Do not create a site just because you think you found high paying keywords and throw content in just based on them just for the purpose of profiting from them.