Before you need to implement your AdSense codes correctly, you should have the following requirement in place.

Good textual content pages.
Your pages should have enough textual content, when you have more text on your pages Google can place ads that are more related to your content. Otherwise if your pages have very limited text then you will end up seeing Public Service ads which won't make you any money.

AdSense Tips

1. Place the ads on the upper part of the page

Don't put the ads on the scrolling side of the page, don't hide your ads on the parts of the page where people cannot see them easily. You want people to click on them right? So put them on visible place, upper part of the page is a good choice, place on top of the page or top right column. Give your ads a proper placement, don't put the content so close to your ads, let your ads stand up from the rest of the content so that it can be seen clearly.

Recently Google has produced a heatmap to illustrate which parts of the page are most effective in placing the ads. Please look the image below. Darker colors illustrate effective areas and lighter colors illustrate the worst areas to place the ads in your page.

2. Use relevant page titles for each page
Do not put the same Page Title throughout your site, rather give different Page Titles for every page according to the content of the page. Keep your Page Titles short and meaningful. Putting too long titles might get your website banned from many search engines, so be careful. Keep the content of the page specific, allocate one page for one topic if possible that way your Google Ads will be more relevant to the content of the page. When you have closely related ads on your page, users are more liekely to click on them.

3. Use your topic name in the url
If you are writing an article about AdSense don't forget to include "AdSense" word in the filename, for example: adsense_something.html Google pays attention to your page names. Putting a relevant page name will increase your chances of displaying more relevant ads on your page.

4. Match the ad colors to your site
You should modify the colors of the ads to match your website design, that way it will be like part of your website and will be easy on the eyes. You can even blend it to your content pages, but be careful making it seem part of the your content is an offense, and might get you in trouble with Google. Google says too much blending is illegal, if you are making people think that ads are part of the content, and if you are making them click unintentionally then you might want to consider the way you are implementing the ads on your website, otherwise one day you might receive a termination of account email from Google. So blend it to your website but at the same time make sure that it stands out from your content and not taken as your website content. Use white space to give it a prominent look.

There are claims that yellow background with red text ads bring a higher click-through, I cannot confirm this at the moment. Try it out and if it works feel free to implement.

5. Use vertical ads and not horizontal
Using vertical ads will bring you more hits, why? Because all traditional ads have been horizontal on internet, 468x60 banners being the pioneers, and people tend to ignore them which is called banner blindness. However when you put a vertical ad on your page "banner blindness" is not that high unlike horizontal ads.

Particularly 120x240 ads perform better on my site, you can see them on the left top column on all secondary pages.

6. Use text ads and not image ads
Banner blindness issue comes here as well, people usually don't pay much attention on the image banners. In this case it is proven that text ads perform better, their click-through is up to 5% while image ads click-through is less than 2%. So use text ads and get better click-throughs.

7. Use channels to monitor your ads performance
Use channels to keep track how different parts of your website is performing. For example you can specify a channel called 'horizontal ad' and run that ad for 2-3 days, and again you can create a channel called 'vertical ad' and implement vertical ads with this channel on your website for another 2-3 days. Then you can compare which ad type has performed better on your site. That way you will know which ad type, size and where exactly to implement different ads.

8. Do not set Google AdSense as a secondary ad option
If you want to maximize your AdSense revenue never set it as a secondary ad option (as a default ad). Because when you set Google AdSense ads as a default ad it will show up inside the i-frame of another Ad Network's panel. And this will prevent Google to scan the contents of the page properly and most of the time it will not be able to show the most relevant ads. Usually it will end up showing one and same ad all over the place. Using AdSense in this manner will reduce your eCPM, as a result your revenue will decrease. Because users are less likely to click on the same ad multiple times.

When I tried out this on my own site, my earnings dropped by 50%, and I was seeing not relevant ads on my pages.

9. Use Google AdSense Preview Tool to remove irrelevant ads
You can download Google AdSense Preview Tool and use it to see what kind of ads are appearing on your pages and to eliminate the ineffective ones. If you see particular ad all the time on your website and if you think that people will not click on it then you better remove it.

Google AdSense Preview Tool will also save you from clicking on your ads to see the urls, which is a very dangerous thing to do. Google has the right to close your account for click fraud. As you know sometimes in 468x60 ads the url of the ads will not display and to see the url of the ad either you have to click on it or use Google AdSense Preview Tool, I would suggest you use the Google AdSense Preview Tool.

10. Use 336x280, 300x250, and 160x600 ad formats New Tip
Try using these three ad formats, because according to Google AdSense Optimization Webinar they are the top performing ad formats. Here is what Phoebe from Google said in the webinar:

The next optimization tip that I'd like to focus on is ad format. … You see our best performing ad format. It's the large rectangle, 336x280. So the wider ad formats are doing better than the other ones and the reason is that they actually take up fewer lines. And so with every additional line, you have a chance of losing that interested user.

So the wider formats do best so specifically, the top three formats are the 336x280 that you see on the page; the 300x250 medium rectangle; and then the 160x600 wide skyscraper.

11. Don't Cheat and Ask Google if you have a question
Lastly don't cheat! Cheating will get you nothing, sooner or later your account will be terminated and all your money will be gone, so play fair. It is illegal to place texts like "Please support us and click on the ads".

Prohibited Uses: You shall not ... encourage any third party to ... generate fraudulent ... clicks on any Ad(s)

Just remember that Google is watching your website and the way you implement the ads on your website.

Ask Google if you have any question or if you are not sure if your strategy breaches their Program Policy. Google's support team is very friendly and fast, just send them email and you should receive answer soon. That way you will be safe from any trouble.

These simple steps will make your Google Ads perform better, if you have any other ways that you have implemented on your site and have seen your click-through rate increase then let me know. And I will be happy to add it here.