Roger Federer succeses, what should I put in my envelope?

[TennisGirl]

Hi,
So I'm really hoping to get a Roger Federer autograph and I'm going to send him a letter soon. I'm wondering what I should put in the envelope? Obviously a letter, but what else? I live in Switzerland too, so if I just put some Swiss stamps in, will that be ok? Or should I also put a SASE in? Should I put my own picture in? And how big should the envelopes be? Thanks!

Sorry for all the questions!