I usually use the same approach every single time before starting any type of side project or testing any new channels. I try to approach growth hacking as lean as possible. If it’s a side project, I try my best to build out a solid foundation and understanding of my potential customers prior to when the app is finish building.
What works for me might not always work for you, but I always start off marketing by asking myself a few questions. I usually write these questions out and try to answer them myself. This will help me validate my ideas and targeted marketing channels.
Interesting post on taking a lean approach to user acquisition.