Instead of promoting your newsletter, get more subscribers by promoting specific content.

It might seem odd, but promoting your newsletter is not the best way to promote your newsletter. Boost subscriptions by promoting specific pieces of content.

Josh Spector of For The Interested has experimented with lots of different ads to bring new subscribers to his newsletter. What he learned was that ads promoting a specific piece of content are far more effective than those promoting the newsletter itself. People are more likely to click on interesting content than a random newsletter, and if they find the article valuable, they often use the signup form at the bottom of the post to subscribe. For best results, you'll want to pick your best piece and make sure it shows off what your newsletter typically offers. While Josh was experimenting with Facebook ads, it would be reasonable to assume that this applies to other platforms and types of promotion too.