Speak their Language
The subject line needs to be relatable to the recipient, otherwise they will never open it. Look to pop culture for great ideas. The most common pop culture categories are: entertainment (movies, music, television, games), sports, news (as in people/places in news), politics, fashion/clothes, technology, and slang.
Jump on the bandwagon
With email marketing platforms, just like all technology, functionality continues to be improved. When your platform provider rolls out a new update, become familiar with it - and use it. Currently, the newest functionality includes personalization and emoji’s in the subject line. They did it for a reason. The research has proven that you are more likely to open an email if it’s personalized. So, in the race to be the industry leader, the top email marketing platforms have figured out how to make this happen. Use it to your advantage. Eventually it will be overused and will lose its impact.
Keep your theme in the follow-up
If you are using an email marketing platform, you know the results of your email campaign. You know what each person did or didn’t do. You can group your recipients by their action and follow-up with another email. For the recipients that opened the original email, keep the conversation going. Don’t confuse them with an entirely new topic, build from the original. Each campaign is a new topic, follow-thru with the follow-up.
The preview text is a snippet of text from within the email. When sending a single email from your email application the snippet is the first line of text. It is a prelude to what's to come. When sending an email campaign from an email platform like MailChimp, they give you an opportunity to customize the preview text to help increase your open rate. You usually access this preview text from the setup menu. Make your preview text compelling so the recipient is even more encouraged to open the email.
Subject lines are an art; for some it comes naturally, and for others, it’s learned. Either way, the better you get at it, the more conversations you will have with existing and potential customers.