Your letter should be composed of three or four short paragraphs. The first paragraph should describe who you are and why you are writing.
The second paragraph should describe your professional skills and academic qualifications. Don't mention details about your skills and schooling that don't apply to the specific company and position.
The third paragraph should explain how you can be an asset to your prospective employer. This is your opportunity to show what you know about the company and how your experience will make for a great match.
The fourth paragraph should request that the company schedule an interview with you or contact you about your application.
End the letter with a brief sentence thanking the reader for his or her time, and then skip two lines. Write "Yours truly." Skip three to five lines (depending on space), and sign your name.