How to get autographs help!

It has come to an age where my children have started to want autographs from celebrities and athletes. When I was a little girl, all you had to do was send an LOR and put it in the mail and wait. Now I’ve heard and done a little research, that you have to include an s.a.s.e. inside another envelope. OR a new way for requesting autographs is through the celebrity’s email (obviously for fan mail). I have a couple questions

For handwritten requests:
How big should your envelopes be?
Will the size of your sase become the size of you autographed picture (or whatever it is being signed)?
If your celebrity’s fan mail address is outside of the U.S. which types and how many postage stamps should you include for your envelope and sase?

And for requests via cyberspace:
Where do you find the celebrity’s email?
Could you email the celebrity’s fan club requesting an autograph (I’ve heard though that the fan club might charge you though for an autograph)

Sorry for all the questions!
Thanks!