Since starting TLDR (a tech newsletter targeted towards the kind of people who read Hacker News, Slashdot, Indie Hackers etc.) in August of 2018, I've been growing it steadily with a combination of forum posting, paid ads, word of mouth referral marketing, cross promotion, and link building. I notice a lot of indie hackers are now trying to start newsletters and since I have a bit of extra time in quarantine, I wanted to give a few tips to people starting out:
There are a few tweaks that led to big improvements in mobile landing page signup rates, adding OAuth (see https://www.tldrnewsletter.com, there are OAuth signup buttons for GitHub, Google, and Twitter, roughly 50% of mobile visitors sign up via these buttons instead of the traditional email field), improving page speed by caching via CloudFlare (the site is blazing fast and it's free!), and automatically focusing the cursor in the email input field (for desktop). In addition, it seems like most modern email marketing landing pages have converged on a very minimalist design that gives users fewer options to get distracted, I used to have the full latest issue of the newsletter on the landing page and that performed a lot worse than the current signup page because people would get distracted clicking on links and never come back.
Getting to the top of Google is generally really hard for newsletters because most of your content isn't inherently super linkable (most of your content tends to be in "archives"). A good way to get a bit of traffic especially early on is to Google things like "Best newsletters for insert your target audience" and reach out to the authors asking to be included (or at least leaving a comment under the article if that's allowed). You may also try piggybacking off of Quora's excellent SEO by leaving answers on questions for people who are looking for newsletters to subscribe to.
Doing cross promotions is a nice way to help out another content creator and get more subscribers, it's really a win win. The way I usually do this is I'll reach out to another tech/developer focused newsletter with roughly the same number of subscribers as me (you can usually find out how many subscribers they have by looking at their sponsorship/advertising page) and ask if they want to run a cross promotion where I add their newsletter as a sponsor in my daily update and vice versa, here is the template I use for reference:
I run a newsletter called TLDR, it's a daily, curated tech news newsletter that's mostly read by developers (sort of Hacker News type of content, but each link also comes with a TLDR). I have ____ subscribers at the moment, with a _____ open rate and ____ click through rate. Since there's almost certainly a good amount of overlap between the audiences for TLDR and _____ would you be interested in doing some sort of cross promotion (maybe a shoutout in my newsletter for yours and vice versa) to help grow both of our audiences?
Let me know if you'd be open to this!
As you get bigger, the cross promotions you do will get bigger as well, so it scales in proportion to your newsletter audience!
Starting out, I spent about $50 a day running ads to get the ball rolling with some subscribers. I found that it's really important to keep the growth momentum up in order to stay motivated with any project. If you happen to have a budget to run some ads, I would recommend looking for places other than Facebook or Google to start with, as those are two of the more competitive, efficiently priced ad marketplaces. Because this newsletter is geared for the Indie Hackers/Hacker News crowd, I started out running ads in places like Reddit (you can bid as low as 10 cents per click for any geo and any topic, there's almost nowhere else you can get clicks from US based software engineers for that cheap!) and Quora (with a small time budget, you can actually pick individual questions you want to run ads on. You may only be able to spend a few dollars a day on a group of 20 questions, but those will be the most targeted ads you can possibly run and will be a super efficient way to stretch your dollar).
Once you get a few thousand subscribers, you may try Facebook lookalike audiences, this is a Facebook ad product that allows you to target users that look similar to your current subscribers. Try to be specific as possible, targeting people similar to people who open or click on your newsletter is better than targeting people who are just subscribed to your newsletter.
If you have any questions, feel free to leave them as comments and I'll respond to as many as possible!