A cover letter is a good opportunity to get across a subtle or personal point that doesn't belong on a resume. You can mention in the letter a particular experience in your life that has special application to the job being offered. You can indicate salary requirements, although I prefer to see that issue dealt with during interviews. You can use the cover letter to indicate that a mutual friend has suggested that you write, or to point out some interesting coincidence between your life and the life of the individual to whom you are writing, or of the company offering the job.
But, as with the resume avoid the temptation to be chatty and cute. A cover letter should be short. It should be direct and to the point. It should indicate that your resume" is attached, perhaps a reason for sending it to that particular person or company (in response to a newspaper ad or through the urging of a mutual friend), and should end with a positive request for consideration for the job and an opportunity for a personal interview. Many personnel experts recommend a closing line: "I will call you in a few days to follow up on this." I have mixed emotions about it. It certainly is an aggressive approach that probably works in a number of cases. It makes me a little uncomfortable, though. In effect, it puts the person on notice and has a certain threatening tone to it. The person knows that he or she will have to deal with you on the phone, like it or not - whether your resume holds any interest or not.
I prefer a follow-up letter, rather than a phone call. The written word is wonderful in that it is placed in front of the recipient and has a chance of remaining there as a reminder that you exist and are interested in working for the company.
Another advantage of written communication is that you have the opportunity to say precisely what you wish, and not run the risk of being caught in a conversation that you're ill-prepared to deal with. Certainly, as things progress toward a specific job, and at least the initial interview has been concluded, the use of the telephone to keep in touch is valuable, but for simple follow-up after having sent a resume and cover letter, I prefer a written note.
Ideally, the best follow-up letter or phone call should be to add something you failed to mention during the interview. This is the most subtle, most effective, and most intelligent way of saying "I want the job."
And one thing more: when writing a cover letter, make sure you have the recipient's name and title correct. Very often, we are not sure of either, which means picking up the phone, reaching the operator at the company, indicating that you wish to send correspondence to Mr. Blaine (or Blane, or Blayne), and asking for the correct spelling of the name and precise title. No one wants to see his or her name spelled incorrectly, or a wrong title used.
Finally, don't lie. Embellishing your cover letter might help get you an interview, but if you get an offer and your references are checked-and they very likely will be - any discrepancies on your cover letter will put you in an extremely bad light. Some people who haven't finished college are tempted to indicate that they were awarded a degree. Avoid the temptation; state simply that you are continuing to work toward your degree, if you are, and leave it at that. Don't overinflate your importance on your previous job. If you do a thorough job of cataloging your accomplishments, there's no sense in running the risk of having your potential new employer discover that you can't be believed and trusted.
Everyone in business knows that a cover letter is prepared to put the candidate's best foot forward. There is nothing wrong with highlighting your best qualities. Be factual, be careful in your choice of words, and when you have a cover letter that has met all the requirements I've listed, use it with confidence and pride.