Read the reviews of some apps that work like the one you could make, take notes of the features users are most happy with, but also take special attention to th

Read the reviews of some apps that work like the one you could make, take notes of the features users are most happy with, but also take special attention to the pain points. What are people requesting that the developers haven't done yet? Reviews are a great research tool. Summarize these killer features users want, and build your app from there.