Include your name and contact information at the top of your cover letter. Try to find out who is responsible for interviewing/hiring someone for the position to which you’re applying and address your letter to that individual. Sometimes this information can be found on a company website or on a business information site like Manta.com. Providing someone’s name will get your cover letter (and resume) further along than the standard: “To Whom It May Concern.” It also shows that you’ve done some research — at least enough to know who’s who at the company.
In the opening paragraph of your cover letter be sure to clarify what it is you are writing about. Are you writing to see if that have any open positions? Are you writing in regards to a specific position? If you saw an online posting, provide the name of the site and the date it was accessed as well as the position title and any additional information that makes it clear who you are and the sort of position in which you are interested.