For an issue to become important in a Congressional office, approximately five letters must arrive in a given week. This number is a bit larger for Senatorial offices. When an AAS Action Alert is sent out, we have heard from Congressional offices that many hundreds of letters (from AAS members only in several cases) have convinced the member of Congress to take action on the issue.
To establish a personal contact, it is better to actually meet with the member's staff in Washington or at their home office. Contact the Policy Fellow for help in setting up appointments or information on particular members of Congress.