I used to team teach. When you have a partner in the classroom who takes equal responsibility for the lesson, the system works very well. It takes some time to reach that stage, though, particularly because respect and rapport must be developed. Both teachers must feel comfortable with one another to make mistakes and offer suggestions.
Here's an interesting article on team teaching that takes the discussion in a different direction. But the tips are applicable to all situations nonetheless.
English Teaching Forum Online – Bureau of Educational and Cultural Affairs
Good luck in the classroom!