I am about to undertake a visual re-design of the site but recently several companies have contacted me about selling ad space on my site. Up until now, I have just thrown in some AdSense text-ads (wherever they fit on the page). Before I do the re-design I want to take a step back and make sure it is both user and advertiser friendly.
Are there any good guidelines and/or resources to help me structure my site with advertising in mind?