Choose an audience for your letter
Choose a person or group to whom you would like to send your letter. The intention of this letter is to try to persuade this person or group to take action on the issue in some way.
Some organizations who might be appropriate for your letters are:
U.S. Congress Committee on Science, An international organization dealing with the ethics of cloning humans, The Department of Justice, The National Institute of Justice, National Committee on the Future of DNA evidence
If your state is addressing one of the bills above, contacting your state senator or congressperson would be appropriate.