"Think about what information is most valuable for your list and how to capture it in the briefest way possible," Turnbull says. "For example, if geographic location is needed, consider prompting only for zip code instead of street address or phone number." An email address is the only prompt you need, but if you do ask for additional information, he recommends you consider making it optional and give some reason or additional incentive for doing so. "You can also get more info later, either directly or indirectly, after they sign up," he explains.

"Subject lines should be less than 50 characters, and that includes spaces," Cates says. The very best subject lines-the ones that get opened the most every time-are the ones that tell exactly what's in the email. Turnbull agrees that good subject lines should be as brief as possible, accurately reflect what is inside and motivate the recipient to open the message. "Ask yourself if this subject would stand out if it was one of the dozens of unread emails in your inbox," he says.

Remember that your email subscribers are people too, so don't be afraid to let your personality show. Good writing really matters in marketing, and one of the email marketing tips Cates says can really make a difference in connecting with customers is to write like a human. "Drop all the marketing and sales-speak. Just like social media, one of the great things about email is that it has allowed businesses to speak in a more casual voice with their customers and fans. This means you can be funny and loose in the ways you get your messages across," he explains. "Write to your readers like they're people, not customers or subscribers, because that's exactly what they are."