I use Newsy to test things out initially. Newsy (
https://www.newsy.co) is a tool that converts a domain name into a content-aggregator (i.e. Reddit clone). Here's what I've been doing.
1. I have an idea for an app. I buy a domain name.
2. Usually, I don't have much time to develop the domain. And while I'm doing all the market research, I plug my domain to Newsy. Newsy asks me to fill in some niche keywords which are related to my idea or startup I'm thinking of. So I type in "workout", "weight training", "workout training exercises".
3. Newsy will automatically find contents and create it (here's an example - security related - https://www.getinfosec.news)
4. It comes with sitemap, newsletter, Twitter integration to regularly post tweets. I also let a few of my colleagues know. Over the next few weeks, it builds traffic. It even gets some people sign up as a newsletter subscriber or member on my Newsy site. Sometimes, I post links on Reddit just to kickstart some traffic driving to my site. It works from time to time.
5. I let it run for about 2-3 months. By this time, I have ~30-50 users signed up with real email address. Now I can actually start emailing these users to find out more about the problem space that I want to solve.
Above process has been super interesting - if anything other than to make sure my newly bought domain is being used, not just sitting there idle. Hope that helps someone.