Each Legislator has a staff of persons to assist in areas of their expertise. You should try to meet with the staff member that is responsible for the area of your concern. When Congress is recessed, the Legislators are usually back in their home states. Each of them maintains offices within their state or district. Contact their local office and arrange for a meeting.
Some Legislators have public meetings around their state or district.
During these meetings you can express a concern, or better yet, have several others present that can support your cause. Again, do not underestimate the power of numbers as the more people concerned about a given issue, the better the chance of prompting action. It is very important that you prepare for this meeting. The broader the base of your support, the more likely your Legislator will listen. Watch your local media and become involved in the beginning of an issue.