You've carefully polished your resume and put together an appealing personal website. You've contacted your references to make sure they're prepared when employers get in touch to ask about you. Now that you've done everything else right, don't neglect to write a stellar cover letter. 

Though most of us think of a cover letter as a formality--basically a note that says, "Please look at my resume"--in fact it's a lot more than that, and it should be crafted as carefully as the resume itself, according to Alyssa Gelbard, founder of the career consulting and personal branding firm Resume Strategists. "A cover letter is your opportunity to showcase why you're a strong candidate," she explains. "It is also a reflection of your personal brand and can contribute to someone's impression of you." It's also the very first communication a potential employer will see from you.

At a bare minimum, double check that you have the person's name and the company name correctly spelled, as well as the correct title for the job you're seeking. Beyond that, here's Gelbard's advice on how to write a cover letter that will act as an effective sales tool to help you land the job or deal you want.

1. Keep it short. 

"You don't need to restate your whole resume in a cover letter," Gelbard says. You may have a lot you want to tell the reader about why you'd be perfect for the job, but limit your cover letter to just a few paragraphs.

2. Include the job title and details about the job.

Why? Because hiring managers often put out calls for applicants for several positions at once. You don't want the person reading your email to have to struggle to figure out which job you're applying for.

3. Mention where you saw the job.

Hiring managers are often curious to know where candidates saw their postings, so they'll appreciate hearing whether you found the job on LinkedIn, the company website, a newspaper ad, or an employment website. They'll also appreciate knowing that you're not applying to so many jobs that you yourself can't remember where you found theirs.

4. If you've been referred, say so.

"If you're reaching out at the recommendation of someone else, always lead with that," Gelbard advises. "This gets noticed quickly and will help you stand out." In fact, if you're sending an email, "Referred by [name]" should be how you begin your subject line

5. Use language from the job description.

You don't want to be too obvious about this--don't cut and paste, for instance. But picking up a few key words from the job listing will subtly convey the message that you understand the job and will be a good fit.

6. Highlight your value.

"Include why you would be an asset to the company and the unique things you have to offer," Gelbard says. You should also mention relevant experience and expertise and anything else a hiring manager might really care about--for example, if you spent 10 years working for the company's biggest competitor. "These are things that entice a hiring manager to contact you for an interview," she says.

7. Show some personality.

It's a fine line--you don't want to make a joke that will fall flat or offend with too much informality. But while it's wise to err on the side of caution, if you sound like a robot, the hiring manager may have no special reason to pick you. "Let your passion and enthusiasm come through, as long as it doesn't sound fluffy or hokey," Gelbard says.

8. Use "Ms.," not "Mrs." or "Miss."

"Don't assume a female contact is married," Gelbard warns. "Ms." is universally accepted throughout the business world.

9. Watch out for crossed genders.

Is your contact's first name Jordan, Morgan, or Pat? You may think you know what gender that is, but you could be mistaken. (I once had a very embarrassing experience with someone named Chris. Because this person worked in a heavily male profession, and because I happen to know more men named Chris than women, I unconsciously assumed Chris was male. I was wrong.)

In most cases, you'll be able to settle any uncertainty by looking the contact up on LinkedIn. If you really can't find out, start your letter with the complete name, as in "Dear Chris Jones."

10. Don't rely on your spell-checker.

All of us are subject to typos that spell-checking software won't catch, such as a dropped word, homophones ("to" instead of "too"), etc. Reread your cover letter carefully, or better yet, have someone else read it before you send it.

11. Double-check the date.

As a last step before you send, make sure the date on your cover letter is current. If you've lifted text from another letter, or you've started the letter several days ago and come back to it, you could be behind the times. And that's not the impression you want to convey.