Whenever possible allow interaction without using the display.
There are apps that require a continuous usage of the screen. However, there are use cases in which the screen can be replaced by less power intensive alternatives.
Allow users to interact with the app using alternative interfaces (e.g., audio).
In a navigation app, there are use cases in which users might be only using audio instructions and do not need the screen to be on all the time. This pattern is commonly adopted by audio players that use the the earphone buttons to play/pause or skip songs.