The cover letter, or letter of application, always accompanies a resume that is mailed. A cover letter may or may not be required for an online posting, so adhere to application guidelines. A cover letter is NOT needed when handing your resume directly to an employer. In general, although a cover letter may not be formally requested, an assumption should be made that it is required.
Your letter must be free of errors and grammatically correct. Do not over use the word “I”.
If the employer asks you to include salary requirements in the letter, always state your requirements in a range, and that you are open to negotiation.
Customize your letter to each organization and match your skills, experience, and personality traits to the position.
Read your letter out loud to ensure that your ideas flow and to catch any awkward sentences or overuse of words or phrases.
Use a business letter format with left-justified margins, and center the letter vertically on the page.
The letter should be no more than one page in length and printed on the same paper as your resume.
For electronic transmission of your letter, employers often prefer certain formats. One of the easiest and most reliable methods is to convert your cover letter to a PDF through Adobe Acrobat Writer.
Source: KSU's Career Services Website