Each of you noticed that some apps have the same elements across different applications. In most cases, those are default UI components that operating system suggests using. These components may be anything from pop up notifications to the controllers like drop-down menus, sliders, back buttons, etc. Those all are native components.
So the #1 thing you need to have at the starting point is an IDEA. A clear solid idea of a solution that will solve a specific problem or will bring a value to the people.