This is the best advice. You should write a book like Joel.com hasPlace Ads Above the Fold
"The fold" is industry jargon for "the part of the page that the user sees without scrolling down". This will vary depending upon the resolution of the users screen and the size of their browser window.
Place as many ads as possible above the fold. Ads placed below the fold are seldom seen and seldom clicked.
Place Ads on the Left
Web users are accustomed to seeing menus on the left side of the web page. Move your menu to the right and place your AdSense ads on the left.