How would I write a legal binding contract?

I would like to know how exactly I would word a contract to get the title to a car I cosigned for. My mother is the primary signer but she has not made any payments on the car and now they are going after me. I have the money to pay off the car completely, but I want to make sure that if I pay it she won't be able to take it away from me and that the title would be in my name only. How would I go about doing this?