Understand that negative things may be said about the script, but they are said to help better the film.
Do not take anything personally. Many clashes occur because comments about scripts are taken too personally.
Show confidence when you need to. If you strongly oppose a suggested change, explain (in detail) why it is there, belongs there, and needs to stay.
Avoid being overconfident. Producers may not be writers but they are not idiots. They ARE right some of the time.
Stay on a producer's good side by incorporating, and being enthusiastic about, some changes she suggests. This goes a long way to developing trust and keeping a relationship strong.
Recognize the give and take nature of your positions. Producers need a script to be a certain way to attract investors and actors. They are not out to change things for the sake of change. Be fair and cooperative, but defensive when you need to be.
Give respect to get respect.