Since the Anthrax postal scare of 2001, e-mail is the preferred option for sending written communication to Members of Congress. E-mail is just as effective as a First Class letter and it is received immediately by the Member's office, not in the six to eight weeks it takes a mailed letter to arrive. Communicating by fax is also an option, although emailed is preferable.

Some specific tips:

1. Try to stick to one typewritten page; two pages at most. If writing a regular letter, don't write on the back of a page. If writing longhand, take care to write legibly. In e-mail, always use proper net etiquette (avoid using all upper case letters as this connotes shouting, etc.)
2. In a short paragraph, state your purpose. Stick with one subject or issue. Support your position with the rest of the letter.
3. If the subject of your letter is a bill, cite it by name and number.
4. Be factual and support your position with information about how legislation is likely to affect you and others. If possible, describe how the legislation will affect people in your Congressional District or state. Avoid emotional, philosophical arguments. Don't flame* or spam** legislators.
5. If you believe legislation is wrong and should be opposed, say so. Indicate the likely adverse effects, and suggest a different approach.
6. Ask for the legislator's views and his/her support, but do not demand that support. Remember, Senators and Representatives respond to a variety of views, and even if the y do not support your position on one issue or bill, they may support it the next time. So, ask for the legislator's views and express that you look forward to hearing from them on this issue soon.
7. If writing a letter, make sure your name and address are legible. In e-mail, make sure your name, full address, and e-mail address are included.
8. In an email or letter, the suggested style is:

The Honorable ___________________________________
United States Senate
Washington, D.C. 20510
Dear Senator ____________________________________

The Honorable ____________________
United States House of Representatives
Washington, D.C. 20510
Dear Representative ________________

(Begin e- mail by Dear Representative ____________ or Dear Senator _____________ )

Next: Contact Your Legislator

*Flame - insulting or derogatory e-mail.
**Spam - to inundate someone with e-mail, usually in an attempt to overload and crash the person's Internet system.

Adapted (in part) from the 1991 U.S. Congress Handbook.

Source: 2012 Disability Policy Seminar, Washington DC