When writing your subject lines keep in mind:
a) Keep it short and sweet! Don't let your subjects run any longer than 60 characters - and make sure that the most important details are mentioned first so it doesn't get cut off.
If your subscribers can't read your entire subject line because it's too long, chances are they won't open your e-mail.
b) If possible, personalize it! A subject line like "Bob, here's the info you need..." is going to get a MUCH better response than simply "Here's the info you need" because the recipient assumes you know them - and is therefore more likely to open the e-mail.
Test, test, test.
Test continually to determine trends and styles that appear to work. Pre-test if you can. Add a day to your campaign-creation schedule to give you enough time to try out different email subject lines.
Open rates don't always measure subject-line success.
Look at the subjects associated with the highest number of conversions, such as registrations, clicks to view newsletter articles, sales or downloads. If you drill down into your web analytics, you might find some incongruities such as an email with a relatively low open rate but a high sales-per-order rate. That could mean something in the subject line strongly appealed to a narrow segment of your email list and could point the way to a more lucrative segmentation. Remember, your end goal is not necessarily high open rates, but to have email subscribers take a specific action. Focus on your end goal.
Urgency drives action.
Set a deadline: "Order by midnight tonight;" "Last day to ensure Xmas delivery." Use urgency and deadlines as part of a planned series of emails as well. For example on Monday incorporate “5 Days Left…” and then on Thursday follow it with “Only 24 Hours….”.
"Free" is not evil.
Yes, you can use "free" in an email subject line. Just don't make “free” the first word, use it in conjunction with an exclamation point, or spell it in all caps (could get your email filtered). People still respond to "free;" so, the increase in orders or other actions will almost always outweigh the email messages lost from filtering.
Lead, but don 't mislead.
Don't stretch the truth in the subject line or promise more than the email can deliver, or make grand claims that readers will find hard to comply with in order to get a special offer or benefit. Readers will distrust you (and reach for the report-spam button) if your subject line doesn't reflect the email content.
Write and test early and often.
It has been proven that personalized e-mail like this can increase the response you receive by as much as 64%! So don't take this technique lightly...
