What do you put/write outside the envelope when sending a fan mail to J.K. Rowwling/?

Question

I already know her fan mail adress address which is:

J.K. Rowling

c/o Scholastic Books

555 Broadway

New York, NY 10012,USA

, so what i'm basically asking is what do we have to write or put when sending a fan mail to J.K. Rowling?

Also, how much stamps do I have to put in the envelope?

(ex. 42,39?)

Answer 1

As with any letter, you put your return address and a first class stamp.