Let content and functionality motivate every design decision: This is a very important guideline that helps create a clean and clear application. Every piece of UI element, interaction, gesture, imagery, animation, video etc. should be deliberately considered, and the app should not be crowded with unnecessary information that users do not need. This goes back to one of the three principles of IOS designs: Deference (the UI helps people understand and interact with the content, but never competes with it).
App should interact with users just like how human interacts with human: a lot of the IOS principles of how an app should be designed goes back to the natural way how a human interacts with another human. For example, an app should maintain a sense of give and take that helps people feel they are making progress as they move through the app. The app should show users the value of the app before asking for login information, and delay login as much as possible. In addition, the app should ask users’ permission before accessing their private data, and clearly state the reason. All of these principles follow a sense of give and take, mutual respect for each other’s privacy and total control.
An important point of the iterating process of conceptualizing an application: (1). first brainstorm and come up with a list of app features (2). Define target users and user characteristics (3). Go back to the list of app features and based on the user characteristics, cross out features that do not meet user characteristics (4). Based on the polished list of app features and user characteristics, draft the app definition statement that clearly defines the target users and the core functionality of the app.