Model positive and negative pair programming behavior by having a student pretend to pair program with you. After each of these role-plays, have students identify the positive and negative behaviors. Ask students "How do you think my partner felt when that happened?" to help students imagine the experience of their partner. It is helpful to model asking a partner for their opinion and checking if they understand. It can be helpful to refer back to a relevant role-play if students are stealing the mouse or bossing their partner around.
Example: "Navigators: are you offering suggestions or commands?"
See this and related tips as a Tip Sheet: http://csteachingtips.org/tips-for-pair-programming