In other words, send a letter to your own Senator, not the one clear across the country that you saw on television. Don't bother sending emails. Your representatives are totally overwhelmed with email. In addition, sending an email is so easy that they have gotten into the habit of just ignoring it. Write legibly or type.
Handwritten letters seem more personal, while typewritten letters appear businesslike.
Choose the proper format for the effect you want to achieve. State your purpose in the first paragraph. If you are writing about a bill, include the name and number. Avoid emotional arguments. Treat them with respect.