Vic Romano said:
I'd think that if you send a SASE, it's obvious, but I always ask very politely if they'd do me the great honor of sending me an autograped photo. Who knows. maybe it is rude and that's why I've never heard back.
One time I read an article on seeking autographs.
It said if you want an autograph you should send a SASE.
Or in your letter you could enclose a postcard for them to sign and send back to you.
The biggest no-no in the article was don't expect a response if the performer is currently hot stuff or in big demand.
In the past, if I saw an actor I liked was in a Broadway show, I would write to him/her care of the theatre a few months after the play opened, (when they are no longer 'hot'.)
The TV and movie unions (AFTRA and SAG) use to forward fan mail to performers. I don't know if they do that anymore.