Wasn't sure exactly how to ask this, but here we go- So, for example, I installed "Dialer One", a dialer replacement. So whenever I hit the "Phone" button, it asks how I want to complete the action. Using Dialer One, or Phone. And it gives me the option to "Use by default for this action". So, lets say I want to use Dialer One by default, but then I change my mind. How do I set it back to the default Phone. Obviously, this question applies to more than just the phone app. After writing all that I think the simple way to ask my question is- I really just want to know how to undo the 'use by default for this action' choices I may make in the future. Thanks!