Ask HN: Things I should include in my letter to my representative?

I would like to write a letter to my representative concerning the recent revelations brought forth by the exposure of programs such as XKeyscore and PRISM. I want to make it as concise as possible, however I don't have much experience writing formal letters, let alone a letter to a congressman. My first and most recent letter to my representative was concerning SOPA and I don't believe my letter was worded well at all. Does anyone have any suggestions about what to ask for / how to express my concerns regarding these programs?

Some Things I would like to include are:

  1. How limits on free speech limit innovation
  2. How trust is integral in a nation [1]

If anyone could give me some guidelines on how to write a formal letter I would appreciate it. Or any other points to include.

Thank you

[1]: https://www.schneier.com/blog/archives/2013/08/restoring_trust.html