The cover letter is your chance to sell yourself to a potential employer as the best candidate for a specific position. As such, it’s just as important as your resume. In fact, you should never send out a resume without one.

The most important thing to remember is that your cover letter serves a separate function from your resume and should not be used to repeat the details of your resume, such as work history, education, or personal objectives. The resume is about you, your experience and your skills. The cover letter is about what you can do for the employer.

An effective cover letter should accomplish three things:

1. Introduce Yourself and Your Reason for Writing The first paragraph needs to grab the hiring manager’s attention. Say exactly why you have sent your resume: you are interested in the company and you want to fill a need they have. Demonstrate your interest by indicating any connections between the employer and yourself. Show that you work in the same field, that you share a common professional interest, or that you have been following the company or industry in the news.

If you were referred to the company by a mutual friend or associate, mention them; the hiring manager may feel more obligated to respond to your letter. (Don’t profess to know more than you do, however. If you make inaccurate statements regarding the company or the industry, the hiring manager will see right through it.) When offering to fill the company’s need, be specific as possible. Don’t just mention the job position, describe what the company requires from that position.

2. Sell Yourself In the second part of the letter state (briefly) the skills you bring to the table that will specifically meet the employer’s needs. There is no need to go into great detail; your resume should take care of that.

Instead, use this section to highlight how you will use your talents and experience to benefit the company. Don’t use it to indicate how you think you’ll benefit from being employed–with a stack of resumes on her desk and positions to fill, the hiring manager isn’t concerned with your personal fulfillment. Keep your use of the personal pronoun “I” to a minimum. Try to use it in this sense: “Here’s how I can help you.”

3. Make a Plan Close the letter by indicating what you would like to happen next. Don’t leave the ball in the employer’s court; take action! Tell the potential employer where you can be reached, either by phone or by e-mail, but don’t wait for a call. Indicate that if you don’t hear from them within a few days, you will follow-up with a phone call to make sure your resume and cover letter have reached the intended recipient, and to arrange a face-to-face interview. Be assertive but polite. (Some job seekers may want to use a paragraph to explain anything that’s not apparent from the resume, such as large gaps in the employment history.)