What you do is you pick a Twilight character and have them write a brief letter to another. The next poster takes the person who the letter is from and writes a letter to them from another character? Get it? Here's an example:
You suck. That is all.
I miss you.
Roses or Tulips for your bouquet?
So you guys get the idea right? Hopefully you guys can think of a better one. Just continue from my post.