They can often be important allies. Writing to a public official does make a difference. They know that every person who writes represents many others who feel the same but don't write. Tell a story or example to make the issue real. Ask for a direct response with his or her position.
Personal letters are much better than form letters or petitions.
Every citizen has the right to seek a meeting with their legislator, councilperson or other elected representative. Make your group diverse. Discuss in advance how to handle the meeting. Be direct but not threatening. Know your facts.