Every resume you send,fax, or e-mail needs its own cover letter.
Sending a resume without a cover letter is like starting an interview without shaking hands.
The best cover letters spark the employer's interest and create an impression of competence.
Cover letters are an opportunity to convey your focus and energy.
Especially for students why may not have a lot of experience, the cover letter is a way to show enhusiasm.
And following up with a phone call shows the employer drive and interest.
Although you should feel free to consult references and models, use your own words when writing a cover letter; don't mimic another person's writing style.