A cover letter should be addressed to the specific company and the specific individual who will process your application. You can usually find this through research or simply by calling the company to find out who you should address your letter to.

The letter should name the position for which you are applying and also make specific references to the company. Indicate your knowledge of and interest in the work the company is currently doing, and your qualification for the position. You want the reader to know

• why you want to work at that specific company,
• why you fit with that company,
• how you qualify for the position to which you applying.
  

In addition to tailoring your application to a specific job with a specific company , the cover letter should also

• highlight the most important and relevant accomplishments, skills, and experience listed in your resume
• point to the resume in some way {"as detailed in the enclosed resume"}
• request specific follow up, such as an interview.