If you’re like most professionals, you probably write dozens of emails a day but barely think about the subject line. It’s an afterthought that you add just before you hit send.

That may work for your day-to-day emails, but you might be making a big mistake if you do the same thing when creating your campaign emails. The subject line often determines whether an email is opened and how the recipient responds.

Here are some ideas to review about creating subject lines:

  1. Write the subject line first: One of the top mistakes people make on email is forgetting to write a subject line. An email with a blank subject line will likely go unread or get lost in a cluttered inbox. Write the subject line before the email so you know it’s taken care of. 
  2. Keep it short: A typical inbox reveals about 60 characters of an email’s subject line, while a mobile phone shows just 25 to 30 characters. Get right to the point in about six to eight words.
  3. Place the most important words at the beginning: More and more people read their emails  on mobile phones. Since you don’t know how much of the subject line will be viewable from a smartphone, it’s important to put the most important information at the beginning. Otherwise, compelling details could get cut off. 
  4. Eliminate filler words: With such precious space, don’t waste it with unnecessary words like “hello,” “nice to meet you,” and “thanks,” which can easily be included in the email’s body. 
  5. Be clear and specific about the email topic: The subject line should communicate exactly what the email is about so that the recipient can prioritize the email’s importance without having to open it.
  6. Keep it simple and focused: Your email should be focused on one action, which should be communicated in the subject line. Offer one takeaway, indicate how the reader can make use of it, and specify how you will deliver it.
  7. Use logical keywords for search and filtering: Most professionals have filters and folders set up to manage their email and probably won’t focus on your message when they first see it. That’s why it’s important to include keywords related to the topic of the email that will make it searchable later. 
  8. Indicate if you need a response: Don’t surprise the reader and ask them to take action in the body of the email – be upfront. If you need a response, make it clear in the subject line by saying “please reply” or “thoughts needed on X topic.” If not, simply start the line with “Please read,” or tack on “no response needed” or “FYI” to the end. 
  9. Set a deadline in the subject line: Especially if you have a lot of information to convey in the email itself, including a deadline right in the subject line exponentially increases the odds that readers will respond. For example, after the email’s topic, you could say: “Please reply by EOD Friday.” 
  10. If someone referred you, be sure to use their name: If you’ve been referred by a mutual acquaintance, put it in the subject line to grab the reader’s attention right away. Moreover, begin the subject line with the full name of the person who referred you. 
  11. Highlight the value you have to offer: If sending a cold email to someone you don’t know, you need a clear statement in the subject line that indicates value and communicates what they’re going to get. Pique the reader’s interest by offering them something that’s helpful. Whether you’re providing a speaking opportunity, a discount, or a service, make it clear in the subject line what’s in it for them. 
  12. Personalize it with the recipient’s or company name: You have to know who you’re sending the email to, and they have to recognize that it’s about them or a subject interesting to them. Using their name or company name is one of the best ways to do that, he says, and makes the recipient much more likely to open the email. For example, you might write, “Increase Company.com’s traffic by 25%,” or “John, see how you compare to competitors.” 
  13. Don’t start a sentence that you finish in the email’s body: If you begin a thought or question that ends in the email, then the reader is forced to open the email. It’s annoying, and since clarity and being respectful of the recipient’s time is the goal, it’s not very helpful. Consider whether instant message, a call, or an in-person chat might be a better medium for your question.
  14. Don’t put words in ALL CAPS: Using all caps may get someone’s attention, but in the wrong way. It’s the digital equivalent of yelling, and your job is to make the email as easy as possible for the recipient to read rather than giving them anxiety. Instead, use dashes or colons to separate thoughts, and avoid caps and special characters like exclamation points.

Excerpted from http://www.businessinsider.com/