Here’s some oldie but goodie advice that’s as relevant in 2012 as it was in 1912: Use the inverted pyramid for your content.
The principle is this: The highest number of people will read the top of the message and fewer as you work your way down the page. Hence the inverted pyramid.
For those of us old enough to remember the days before email marketing, those days when magazine ads and direct mail postcards were the norm, the inverted pyramid was how your crafty copywriter approached the content. Assuming most people would read the headline, then fewer the subheading then even fewer the beginning of the body text, and so on, until the fewest number of people made it to the bottom of the page or postcard, the copywriter would put the most important information first.
This same approach so commonly used in print can be used for emails too. Once people get past your From name and subject line, you hit them with the most important information in the Preview Pane in case that’s all they see. If they do open the email, assume many will only look at the headline and work that. Then continue to work your copy in such a way that if the reader since only the top part of this upside pyramid, they’ll still walk away with your message.
Be an email expert: Flip your content around with the inverted pyramid, and make sure the important info gets seen.