An agreement is an intention you declare to another person or group; a commitment is an agreement between yourself and the universe.  Every broken agreement or commitment takes personal energy and creates a belief in your ineffectiveness.  An impeccable agreement is one you want to make, and it includes the actions you will or will not perform, and the timeframe in which you will or will not perform them.  One key to making impeccable agreements is knowing how to change the ones that no longer fit, and how to clear up debris from any broken agreements.  A good place to start is:  "I'd like to change my agreement about... My new intention is... Do you have any  thoughts or feelings about this?" 
The Basic Shift:  Acknowledging Desire
In order to make an impeccable agreement you must be aware of current reality and what you want.  While thinking about a certain area of life, complete these sentences: "how it is, is..." and "what I want is..."  Do this as many times as you wish, finishing each sentence with whatever comes to mind.