Simplify the functionality
Identify a single purpose for your application. Try to identify the one goal that you want your application to achieve, and then design your application to support that single purpose. For example, the main purpose of an application that manages pictures might be to "remember that moment."
As you identify the goal, you might need to make some tough decisions. For example, if the main purpose of your application is to allow users to view pictures, make sure you limit the functionality that you provide on the screen only to the features that make viewing pictures a fantastic experience for users. Where possible, move the functionality that is not essential to the primary workflow to a menu.
If you are porting an application that is designed for a computer to the BlackBerry® PlayBook™ tablet, simplifying the functionality might be a challenge. Design your application to include the essential features for mobile users. Provide only the features that people really care about.
Constrain user data input
You should constrain data input for your user as much as possible. This could be as easy as opening the numeric keyboard for a user to type a phone number in a field or capturing data using other means, such as Bluetooth® enabled sensors, cameras, accelerometer, or GPS. Input constraints can reduce the burden on the user and greatly improve the usability of your application.
Another way to support user data input is to make sure that you combine similar input operations together in the flow of your application, so that users don't need to change input modes or navigate to another screen. For example, a mapping application might allow a user to place landmarks on a map. You could allow the user access a menu, choose a landmark tool, reactivate the map content area, and then place the landmark. But a better solution might be to allow the user to simply touch and hold the desired map location and have your application place a landmark pin at that location after a few seconds.