Guidelines for Names and Titles: The salutation should typically use the person's last name, along with a "Mr." or "Ms." In general, avoid using "Mrs." or "Miss" unless you are certain of how the woman wants to be addressed. When in doubt, default to using "Ms."
Example: During the recent ARRGH convention in Washington, D.C., one of your sales representatives, Dusty Brown, informed me of a possible opening for a manager in your Data Center. My extensive background in programming and my master’s degree in information systems make me highly qualified for the position. In subsequent paragraphs, expand on the qualifications you mentioned in your opening. Add any appropriate details, highlighting experience listed on your resume that is especially pertinent to the job you are seeking. Close with a request for an interview. Proofread your letter carefully.