A good subject line is like a good tweet: it earns a click to read further.

We tweet links that amuse, outrage or inspire us. We write our tweets to get others to click. And sometimes we’re more effective than others.

Your subject line has the same mission: earn a click to open the email. The same principles prompt this response for both tweets and subject lines.

So how do you write effective “click-this” text? The Nielsen Norman Group just unveiled the answer ^[1]. Let’s look at how you can apply it to your subject lines.

Start Off Right

See how early you can position your hot topic keywords in your subject line.

This not only catches the attention of subscribers skimming through, it works well when designing for mobile email ^[2], which has a relatively short subject area.

“This email is about your child.” For an audience of parents, there is no greater incentive to click.

Provide Eye-Catching Context

There are millions upon millions of products and services for sale online. Give your subscribers reason to pick yours – offer value beyond the product itself.

Suggest an unusual and helpful use for your product. Link your service to current events. Surround your products with context that fascinates your readers.

Yes, I do wonder how celebrities look so good – are you saying your clothes can make me look that good too?

Keep it Short (Enough)

The right length for a tweet is long enough to make the point, short enough to be usable. The same is true for your subject line.

Only the first 25 or so characters are usually guaranteed to display on computers. Mobile email shows even less.

Test your message in different email clients to find out if enough of your subject fits into the allotted space – you may even find you have extra space you can make use of.

“$5″ and “now”. That’s all I need to know.

Make Every Word Count

The fewer words you use to get your point across, the better. It’s especially important to suck out vampire words ^[3].

Be careful, though – don’t chop words you need. Nonsensical subject lines might grab attention, but it’s probably the wrong kind.

For even more punch, work in romantic words ^[4] or heroic language ^[5] to fire up sluggish subscribers.

Who doesn’t want to be a rock star? And I can get work done at the same time? Even better!

Keep Your Focus Clear

Tweets and subject lines both have a brevity that demands simplicity.

Even if you have several articles or offers in your email, don’t try to highlight them all in your subject line. Pick your strongest selling point.

If you’re unsure which that is, run a split test ^[6] and note what works best for next time.

DD was also running a create-the-next-donut game and just launched a new mocha line, but they avoided overload by sticking to one focus here.

Don’t Forget the Law

Writing eye-catching text demands a certain level of creativity, but it’s important to keep from going overboard. To stay safe, bump your subject line against the ultimate test: the law.

According to CAN SPAM ^[7], misleading subject lines are actually illegal, so make sure yours accurately reflects the focus within.

Please Unveil Your Own Answer Below

Nielsen Norman’s study shows us a big picture based on hundreds of examples. But you’ve got your own story about what’s worked for you.

How do you write an effective subject line? Do you have formulas you stick to or strategies you use?

Let us know in the comments section below!