what questions should I ask the birth mother?

I am scheduled for my first phone call with a birth mom. What questions would a birth mother want me to ask her? Also, I am fearful (for me) that she may decide to keep her baby after it's born. How often does this happen? What would a birthmother want to hear from me, to help her make the decision to place her baby with an adoptive parent?thanks so much-jen.:flower: