Ask HN: What did you do to ensure product viral growth since launch?

I’ve seen a plenty of resources on how to design your product/business to account for networking effect or effective word-of-mouth tactics to make your user base grow once your product is out there. I wasn’t so lucky to find many case-studies describing what successful teams did to get initial seed of customers right away after launch. I found an interesting case-study about how Slack did it (http://bit.ly/2RtKIDO) and I’m curious if you have similar stories to share. Thanks!