If you are starter, you’d better visit Google AdSense site to get a comprehensive understanding of AdSense optimization tips. It is located here:
The following is a summary of most important tips to get best performance of your Google AdSense:
1. The beginning of primary content is the best place to show ads. Next is the right side of your web page where typically a navigation menu is placed.
2. Try to use the same color of ad as your primary content.
3. Use more than one ads units in different ad format if your content is text-rich.
4. Create as many channels as needed to track and improve ad performance.