A great cover introduces you to an employer and entices him to invite you in for an interview. A cover letter should always accompany the resume; it lets hiring managers know which position you're applying for and it gives you a chance to display your personality. Use your cover letter to explain something you can't fit on the resume, such as a gap in employment or a plan to relocate.
Keep it short. Hiring managers have a lot of applications to read and they'll probably pass over something long. Use three short paragraphs for your cover letter with no more than three sentences in each.
Begin your letter by explaining how you found the opportunity and what interests you about the job. If you were referred by someone such as a company employee, be sure to mention that right away. You may also mention something positive you read about the company or how your skills and experiences relate to the position.
Use the second paragraph to explain exactly why you're the best candidate for the job. Relate your accomplishments to the position. Don't use cliches such as "I'm a hard worker" or "good communicator." Instead, show the hiring manager these qualities in action. For example, "With my time spent managing sales staff, I know I can bring good people skills and leadership to your company."
Also in the second paragraph, list two other qualities or experiences that relate to the position. Use examples and be specific.
Close the cover letter with a third paragraph that asks for an interview. Tell the hiring manager that you look forward to a meeting and leave your contact information such as an email address and phone number. Finish the letter with a professional closing such as "Sincerely." Sign your name.