Three seconds and 40 characters. That's all you usually have to work with when trying to get and hold the attention of someone reading email. And, with user behavior changing so much in response to overwhelming amounts of spam, the attention spans of email readers are getting shorter. Needless to say, it's vital to make the most of your introduction via the email subject line.

Email marketing powerhouse DoubleClick.com conducts annual surveys with regard to user behavior when it comes to email. A couple of the statistics from their latest findings are interesting. The second biggest motivator in opening email is the subject line. (The first is the "from" line.)

Because subject lines are often truncated at around 40 characters -- and because email readers usually have their index fingers poised over the delete button -- we're left with about three seconds and approximately six words to make an impression. So what works? Which types of subject lines have proven to be successful? Here are my top three.

Make An Offer

It's an old sales cliché that still holds true in the fast-paced world of cyberspace: Lead with your best offer. Whether a product, a service or a proposal, you want to tell people up front about your deepest discounts, your fastest delivery or your grandest idea. Get their attention right off the bat, and you'll likely have your message read. (It's even better if your offer happens to be time sensitive.) Examples include:

Half Off Leather Boots Until March 1st

Top 10 Reasons to Attend [Whatever]

Your Link on High Ranking Web Pages

State A Benefit

Since the majority of consumer and B2B customers live in the "what's in it for me" world, benefits always make powerful subject lines. Telling the readers what the end results of their actions will be helps them visualize the need for your product or service. Here are a few examples based on the subject lines above:

Wear Fall's Hottest Trends for 50% Off

Learn [Whatever] in Only Two Days

Build Link Popularity & Traffic for Your Site

**************************************************

LEARN TO INCORPORATE KEYWORDS INTO YOUR COPY THE "RIGHT" WAY

Copy that ranks high is great... IF it sells. After all, what good is copy that ranks high but doesn't make you any money? To have great SEO

Costly New Prostate Cancer Drug Works In Mysterious Ways
A new prostate cancer treatment that uses a patient's own white blood cells to effectively create a personalized vaccine has been approved. But no one really knows how it works.

Budget Crunch Hits Atlantic City Hard
State and local governments have cut 242,000 jobs since the summer of 2008, and that number is expected to grow as many states face massive deficits. Atlantic City is trying to shore up its finances by firing cops and city workers. Nationwide, these layoffs are causing a drag on the economy.

**************************************************

Evoke Curiosity

We're all nosey to a point. Our curiosity gets the best of us, and we want to know more. That's not only true when it comes to watching movie previews on TV. It's also true for email as well. Some of the best subject lines hook readers by piquing their curiosity, and then reel them in to read the entire message.

Are You Still Wearing These Fashion "Don'ts"?

The Secrets to [Whatever] Never Before Revealed

Link Popularity Scams You Should Avoid

Of course, the key to writing the best subject lines is knowing your target customers, making the topic relevant and testing, testing, testing.

I mentioned a "couple" interesting facts from the DoubleClick email survey. The second is that relevancy is a major player. Over 55% of respondents said they deleted email that wasn't relevant because they considered it spam. DoubleClick also reported that the average open rate was 27.5% (for text or HTML messages). That gives you a baseline to gauge your success.

Not every type of subject line will work for every campaign. Testing is vital. And it's easy enough to do. One of my favorite ways is to set up a Google AdWords campaign and judge the clickthrough rates. This quickly (and cheaply) tells you which subject lines will work and which won't. You can also test your subject lines by sending your emails to a smaller test list before broadcasting it to the entire group.

Whichever styles of subject lines you choose, make sure you know your target audience so you can develop relevant subject lines. Then test and test again until you've created subjects that are highly persuasive and deliver record-breaking open rates.

About the Author

Copy not getting results? Let Karon teach you how to write SEO copy that impresses the engines and your visitors at http://www.copywritingcourse.com. Having trouble working keyphrases into your copy? Check out "How To Increase Keyword Saturation (Without Destroying the Flow of Your Copy)" at http://www.copywritingcourse.com/keyword.