WHAT WE THINK ABOUT WHAT YOU THINK ABOUT.
Here's a little help for clients and copywriters: I learned it from Anne McFadden, my creative director when I was a kid in Pittsburgh. I think she learned it from a guy at Ketchum, who learned it at Ted Bates.
Check it out. In 29 seconds, at a conversational pace, a professional announcer can say...69 words. So, count 'em up. For a 30 second spot, that's all you get.