Rule 5: Don't use other media's design principles.

Of course, design don'ts could fill many pages. But in general, when designing an email campaign, repurposed collateral simply will not work. Marketers need to develop their creative specifically for the PC and for the phone, every time.

One retailer learned this lesson the hard way when the same team that developed the company's weekly circulars tried its hand at email. The retailer then decided to conduct eye-tracking testing on the email creative that was designed in house. Results showed that readers couldn't easily scan the emails, and CTAs and offers were overlooked. In addition, the emails the company tested were so similar in look and feel that the team learned only what not to do, instead of gaining insights into what actually works.

Also, don't forget to QA your emails like crazy. Be sure your messages are actionable with the images turned off. Test text-only emails from time to time. I know of one retailer whose text-only emails routinely make it into its top-five performing emails every year.

Rule 6: Don't miss the inbox.

It seems obvious, but it always bears repeating: Don't forget to comply with global spam regulations. Remember to manage and optimize your sender reputation as though your career depends on it. Partner with an email service provider who's a leader in getting its clients' email into the inbox and opened.

During your quarterly reviews of your email program, be sure your deliverability is optimized. There's likely more you can do in this respect than you may realize. For example, we began a new relationship with an email marketer who experienced blocks at many ISPs during 2007's Black Friday and Cyber Monday. A systematic revision of the company's opt-out, ECOA, subject lines and targeting buoyed its campaigns to 98-99 percent deliverability. Revenue was up 30 percent over the year-ago period -- even in this economy.

Rule 7: Don't disrespect the customers' time and attention.

It's simple. Once your email has arrived, it better be worth the recipient's time. So test your subject lines like crazy. Be clear, stand out and get read. Apply the lessons outlined earlier in this article, and you will see improvements.

Rule 8: Don't forget to apply what you've learned.

Every email you send teaches you something. Make sure your whole team knows what's working and what can be improved. Now is an excellent time to take stock. Early third quarter this year, we sat down with a retail client for a review of all its 2008 email testing. After careful review of the top performers and underperformers, we implemented the changes to creative, layout, subject lines, frequency and targeting that we believe will enable the retailer to have a successful 2008 holiday season. By taking a holistic approach to testing, you won't lose sight of the big picture with each week's mailing.

Keep these ideas in mind as the weather turns colder and "It's a Wonderful Life" begins to appear on TV screens, and you will enjoy a great holiday season -- at least in the inbox.

Chris Marriott is vice president and global managing director for Acxiom Digital.