Use fonts that are easily readable. If your audience can't read your message, they won't act on it. To ensure readability, your font must be large, simple and easily seen. A 12 point font is the minimum size you should use. Anything smaller will be difficult to see. Basic fonts, such as Arial, Verdana and Tahoma, are much easier to read than specialty fonts. Finally, dark fonts on a light background will also be more visible to viewers. These three points will ensure your audience can quickly read and understand your message with little effort.

Apply colors that speak to your audience segments. Did you know both men and women prefer blues and greens, but more women are into purple and more men favor black? Also, as we age we respond to green less and purple more.

Incorporate buttons and links so more viewers will convert. In direct response advertising, big, colorful buttons prompt action. You can use the same button in your e-mail more than once. Just make sure the button's call to action is clear, concise and readable. Also, not all e-mail clients will show your beautiful button, so be sure to add plenty of big blue links in your e-mail so your audience knows exactly where to go.

Write an e-mail with broad appeal. Some will skim your e-mail and others will read it. Skimmers don't read and readers don't skim. The skimmer uses the top of your message, headlines, subheadlines, bolded words and bulleted lists to determine if he will take action. The reader will comb through every word of your e-mail before deciding to act. To speak to both, your e-mail layout should be easily scannable but have lots of meat.  

Use the format that is likely to grab your audience's attention. Statistics indicate that B2C businesses typically send postcards and B2B businesses usually send newsletters. But in practice, the opposite is most likely to be more effective. Consumers respond better to newsletters while businesses are likely to respond better to postcards. So what should you do? Mix it up. The fact is, recipients are likely to respond to what they're not expecting.

Lead viewers to the call to action with a direct eye path. When looking at a document, our eyes naturally start at top left scan diagonally downward to the bottom right. Your e-mail's design should take advantage of this "eye path" movement. That's because studies indicate designs with a clear eye path will get clicks. As a result, the top left of your e-mail is vitally important. It's the place where you build your brand's credibility with a logo. In the same vein, the bottom right is just as important. You should use that space for your offer with a call-to-action button and link. Because most e-mail viewers first look at their e-mails in preview panes, you should remember to repeat this offer, button and link at the top right, adjacent to you logo. This enables your recipient to see your logo—i.e. brand—and offer—i.e. call to action—together in their preview pane.

Make your e-mail readable with and without images. Outlook 2003 introduced the idea of image blocking to protect users from spam. Because of this, business professionals automatically have their e-mail's default preferences set to block images. Because of increased security concerns, today's consumer-dominated webmail clients now share the image-blocking trend with the e-mail user, too. Thus, image blocking has created an entirely new level of complexity for legitimate e-mail marketing. In carrying out your e-mail marketing campaigns, this simply means designing smarter. It's okay to have images, logos, illustrations, buttons and colors in your e-mails, but make sure you supplement them with alt tags so your readers can identify what may be have been blocked. Clear text above the masthead and large blue links throughout the message will ensure your message still gets through, even with certain elements missing.

E-mail clients often strip out vital code. It's risky to use forms, flash and background images in e-mails. Doing so could do one of two things: cause the e-mail to look unappealing to the viewer and potentially cost you a click, or cause an e-mail client to flag you as spam and delete your message altogether. The safest thing to do is use font tags, standard gifs and basic single column tables.

Make sure your message fits in the browser. Because e-mail browsers render e-mails differently than Web browsers render Web pages, e-mail marketers should limit their pixel size to 500-650 pixels wide, the size that most e-mail services present e-mails.