What are some subtle strategies you have found effective in getting people to use your apps?

Different for every app I'm sure, but I have a little one I discovered recently-- I made an app that people really loved once they started using it, but it was difficult to get anyone to sign up. I found that repeatedly showing off the product in a variety of contexts eventually triggered a sort of FOMO, and made people want to learn to use the app, and at that point they would get hooked. Does anyone else out there with a great marketing mind than I have similar strategies they've discovered over the years?