There are many HN discussions with practical steps for startup marketing.

Side Project Marketing Checklist

・ https://news.ycombinator.com/item?id=15002079 (Aug 2017, 68 comments)

・ https://news.ycombinator.com/item?id=14942902 (Aug 2017, 68 comments)

Ask HN: Building a side project that makes money. Where to start?

・ https://news.ycombinator.com/item?id=14039135 (Apr 2017, 248 comments)

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A couple more free resources:

Getting Real, chapter 13: Promotion (2006)

・ https://gettingreal.37signals.com/#ch13

Growth Hacking: How to Acquire Users (2017)

・ https://www.julian.com/learn/growth/intro