1. Put your content's most interesting words at the start of your subject line. Especially as mobile takes center stage in our online lives, readers may not see more than the first three or four words of your subject line. Don't waste precious space by telling them the time and day and that -- surprise! -- you have news for them.
2. Don't duplicate your From field or your Sent field in your subject line. Duplication wastes an opportunity to engage your audience.
3. Put standing identifiers like "Breaking" or "Alert" in your From field, not the subject line. Then your subject line can get right to work on the unique substance of each message. The repetition of those words makes your dispatches look the same, so any one that disappoints a recipient leaves that person less inclined to open the next identical-looking one. Varying your subject line gives you a fresh hook every dispatch. It also helps engage users who unplug for a few days and return to find a list of identical subject lines. What's your reaction to a list like this? Open them all ... or open none?
Take a look at these two lists. Compare them to the lists cited earlier. Which seem most inviting?
Note: These three rules are aimed mainly at marketing- or news-based email campaigns. Of course, they make sense for personal email communication, too. But you're smart enough in your personal work not to use a subject line like this. Why aren't so many businesses that smart?
This hardly covers the subject of email engagement. Read more here: Charlie Meyerson on Web metrics. Does your communications strategy need an update? The doctor is in.