Let's say somebody wanted Oprah Winfrey's autograph. She does books signings, so you might look on her website to see where she's making public appearances, stand in line, and ask her. If you're too shy, you could write in and request one, but she gets lots of requests and definitely has an autopen. You would be amazed at how many celebrities actually read their fan mail, so if you write an interesting letter, you might very well get an interesting response back. I am sure Oprah Winfrey has written many interesting letters, so you have nothing to lose except postage.
For more info on autograph collecting:
http://hobbies.expertvillage.com/interviews/autograph-collecting.htm

hey there does anyone knows how to get an authentic auograph from beatrice arthur?
well cya all,

jelmer