The Preheader references the area before the main content. It's an excellent opportunity to grab a bit of extra pre-content web real estate. It's got a degree of prominence in the inbox, so it would be a waste not to use it for promotional purposes. Try popping a couple of links in here. Some companies find that they get the most clicks on links within their preheader
Whenever possible, add a personal element to your emails. Most email tools allow you to enter shortcodes that will be replaced with the recipient’s name when the email is sent out. Emails from Treehouse Co-Founder Ryan are always fun and personal. The subject lines are creative, messages are sent "from" Ryan's email address, and the content is personalized. If you reply to the mail, you'll even get a prompt response from Ryan himself!
Are you willing to alienate people who disagree with your opinion? Sure, not everyone who disagrees with you will unsubscribe. But if you can’t take the risk of alienating a large portion of them, it’s better to avoid the topic. The only exception are friendly disagreements. For example, it can be a good idea to show your support for a specific sport team, even if you know many in your audience like another team. As long as they don’t take the sport very seriously, it can be just a fun thing to talk about. I could, for example, tell that I’m more of a dog person (we have two dogs) than a cat person. I have nothing against cats, but I like walking with dogs. I doubt almost any cat person will hold that against me.
Personas provide a multi-dimensional method of targeting. They’re based, as the name suggests, on a projected persona for each customer ‘type’. Get it right, and personas can help you enormously in both predicting behaviour and personalising your communications. Personas are a powerful technique, and they’re increasingly used to improve the usability and customer centricity of communications.