“On the average, five times as many people read the headline as read the body copy. When you have written your headline, you have spent eighty cents out of your dollar.” David Olgivy
It's a famous saying, but is there any way to further quantify what makes a successful headline? KISSmetrics author Bnonn cites usability tests which concluded that readers scan headlines, and take in only the first and last three words. Limiting a headline to only 6 words is of course not always feasible, but the advice is to make every word count, especially the first and last three.