Last, but not the least; this is an important question to prevent loss of time and money due to failure and ensure app success. Think about how you plan to handle any adversities!
One way to do this is to understand users and analytics first. This will provide great insight into building the right app. Define your marketing strategy, both initial promotion plan and continued or perpetual to achieve steady growth.
To provide the best app experience to the users, it is a must to provide regular updates as per the response that your app gets! So, plan how often you should release updates for the app.