Sending pictures seems to be the norm nowadays but in the past it was almost exclusive of collector's to send an SASE and receive a photo. \
Just be careful to do research on secretarial, pre print, autopen and similar non authentic signatures.

You can do either. Some people prefer to send their own pictures or memorabilia, whereas I personally just ask for them to send me a signed photo. Either way will work if you send a nice letter Good luck!

Do I have to send a picture? Or can I just request a headshot? I don't have a picture, so if I need to send one in order to get an autograph, where could I find one? I'm trying to get this for my father-in-law who is a HUGE fan.