How to organize a cover letter
Below is one possible way to arrange the content of your cover letter.
Opening Paragraph
State why you are writing.
Establish a point of contact (advertisement in a specific place for a specific position; a particular person's suggestion that you write): give some brief idea of who you are (a Senior engineering student at UW; a recent Ph.D. in History).
Paragraph(s) 2(-3)
Highlight a few of the most salient points from your enclosed resume.
Arouse your reader's curiosity by mentioning points that are likely to be important for the position you are seeking.
Show how your education and experience suit the requirements of the position, and, by elaborating on a few points from your resume, explain what you could contribute to the organization.
(Your letter should complement, not restate, your resume.)
Closing paragraph
Stress action. Politely request an interview at the employer's convenience.
Indicate what supplementary material is being sent under separate cover and offer to provide additional information (a portfolio, a writing sample, a sample publication, a dossier, an audition tape), and explain how it can be obtained.
Thank the reader for his/her consideration and indicate that you are looking forward to hearing from him/her.