Sarah or Sadie??!?!!??!?

My name is Sarah. I like my name, but I hate that it is so common! I know some many Saras and Sarahs and even a Sera and Cera. I am going to be moving to a new school next year and was toying with the idea of getting my new peers to call me Sadie. How would I go about doing this and how would I get my family to call me Sadie too? Sadie is a nickname for Sarah, but some people don't know that.