There are some general recommendations to keep in mind when contacting your elected officials. In many offices you'll be reaching a staff person. The more local the representation the more likely you'll reach the official her/himself.
Whether calling or writing, stick to one topic or issue that is of concern.
Let the staff person, or official, know you are a constituent, and share your zip code. You can also share your name and city if you like. If you vote you can tell them that too.
Share your position or state your concerns. Be clear about what action you would like the elected official to take.