I'm an IT pro who writes website content for software and web developers.
Would you believe it's email? In the era of Facebook, Twitter, and Snapchat, it's easy to assume that social media drives more sales than it actually does. Social media can be useful for marketing, but the easiest and most effective way to reach your customers is to show up in their inboxes. 91% of US consumers check their email at least once a day. And not only that, but 77% of those surveyed preferred marketing efforts to come to them via email, as long as it's something they've opted into. Your customers want to know more about what your business can do for them.
One thing to keep in mind is that about half of all email is opened on a mobile device. That means that your email newsletters and your website absolutely must be optimized for mobile. In a survey by Google, 61% of users said they would not return to a site that was not mobile-friendly. You'll be linking from your newsletter to your website, so view the newsletter on your phone and test the links. What is the user experience like? Is it easy, or is it frustrating? Your goal should make it as easy as possible for your customers to buy your product or service.
Email marketing is effective when it reminds your customers that you are still the solution to whatever problem they came to you for when they subscribed to your email list. Offer them something of value in every newsletter, and in return they'll keep reading—and buying.