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.