Email subject lines are soooooo important!  A poor subject line can mean that your email never gets opened and never gets read. An email that never gets read can’t help you to make a sale, or build your brand with a potential customer, or tempt that new diner to visit your restaurant.

But writing an attention-getting subject lines can be difficult. People are busy, they receive lots of emails and so it’s easy for them to hit delete – if the headline isn’t engaging.

Getting Attention – and Keeping It

The copywriting trainers at American Writers & Artists recommend the following approach to writing subject lines:

1. Be USEFUL to the reader
2. Provide a sense of URGENCY
3. Convey how the benefit is somehow UNIQUE
4. Do it all in an ULTRA-SPECIFIC way

The subject line, is a hook. It must grab the reader’s attention – fast. It should also give them a good idea about what’s in the body of the email. It needs to be specific and compelling as well as attention-getting.

Here are five tips for powerful subject lines:

1. Provoke their curiosity: When you make a headline mysterious enough, the reader will want to read more. That’s why you see emails and banner ads that promise “One weird trick for longer hair” or “Banks don’t want you to know this.” Your mind instantly wants to know what it is, even if you don’t really need hair care tips or reduced interest rates. Likewise, subject lines and headlines are often posed in the form of a question. But if you make it too confusing or cagey, you can risk alienating your reader.
2. Shock them a little bit: If you want to get someone to read an email about the benefits of a desk that raises and lowers, you could write a headline that says “Stand Up at Your Desk for Better Health.” Or you could get scary: “Is Your Chair Killing You?” Use this tactic with extreme caution. Your terrifying headline could murder conversion rates. You can also bring it down a notch and provide a sense of urgency using time limits (“Offer Ends Soon”) and scarcity (“Get One of Only 10 T-Shirts Left”)
3. Use humour (sparingly): Before you dive in to being funny, consider how it reflects on your brand. Is this a laughing matter? Are you at risk of offending someone? By all means add some wit and humour into your copy, but do it carefully. It’s very easy for a joke to fall flat or offend someone.
4. Unpack your adjectives: When you’re trying to write short copy, sometimes adjectives get the axe. Don’t let it happen! They’re the frosting on the subject-verb cake. In the examples below, we don’t just promise you healthier skin. Your skin will glow. We don’t just offer plain old cleansing tips. They’re from professionals. Adjectives are hard to argue with, but you should also base them in reality. Notice we didn’t say “healthy” skin. That’s hard to promise. But it will probably get “healthier.”
5. Focus on the benefit: When in doubt, remember to focus on the benefit to the readers. Why should they care? What’s in it for them? Many writers sometimes jump in and start creating clever headlines without really thinking about what matters to the people reading it.

Formula for a Great Subject Line

There’s no magic trick to creating a great headline. But there are some basic formulas:

• (What they want) + (when they want it)
  Example: Get Healthier, Glowing Skin in 7 Days
• (What they don’t want) + (How to avoid it)
  Example: Prevent Acne with 7 Professional Cleansing Tips

You get the idea. But since every person is different, your approach needs to be different as well, depending on your business type and the customer you are trying to attract. Start with the formula, but test your execution. Most autoresponder software will allow A/B testing so you can test two (or more) subject lines and see which gets the best response.  This will help you to find out what type of subject works best with your audience so that you can create better email subject lines each time you email your list.

Adapted from http://www.business2community.com/brandviews/act-on/5-tips-writing-life-altering-email-headlines-0985707