Highlight your best features. The cover letter resembles lighting in a theater. It illuminates the key parts of your resume, so they make the biggest impression. It also lets you emphasize the fit between yourself and the position. Remember, the firm isn't looking for the most impressive candidate overall. It doesn't want Albert Einstein for COO, as luminous as he might be. It's looking for the person who can best carry out the position.

Be brief and relevant. A very long cover letter suggests a wandering mind and a wagging tongue. It also implies you don't understand the purpose of the letter, which is simply to introduce yourself, underscore points of interest, and seek action.

Follow a four-part structure. In general, the letter should follow this framework:

• Introduction. Provide your name and, if helpful, your position.
• Your goal. Indicate the position you seek. You can sometimes fuse the first two parts into the opening sentence.
• Your key qualifications. Present outstanding qualities or achievements that will pique the employer's interest.
• Request for action. State that you'd like an interview or the job itself. While submission of the resume implies that goal, make your interest clear. An explicit invitation is stronger than an implicit one.

Of course, shape this letter to the circumstances. There are no structure police.

Use a prose style different from that in the resume. Make it easily readable. Favor short sentences, which enhance clarity. The resume may address somewhat complex topics, but don't do it here. Favor short paragraphs too, which can help drive home a point. Don't repeat phrases word-for-word from the resume. You'll seem lazy or unimaginative, and you can always find a way to restate ideas. Depending on the job, you have an opportunity to be warmer, but keep the letter focused on business.

Avoid puffery, cliches, and chest-thumping. They are no more helpful here than in the resume, and may be worse.

Address it to a person, not a title. The recipient is a human being, so make personal contact. Research the name of the hiring authority if you don't know it. If the company hasn't revealed it, you'll create a smart impression at the outset and gain an edge over other applicants.

Make sure all key information is also in the resume. The resume tends to circulate while the cover letter doesn't, and the two may become separated. Moreover, omitting vital points from the resume makes you look careless.

Proofread it carefully and ask a friend to read it. As with the resume, one typo can doom you. And a friend may spot ambiguities in your language and suggest points to add or cut.

Adapt it to other contexts. These principles work generally for the variety of letters you will write, from the thank-you note to the personal contact letter to a company acquaintance seeking background. You simply have to contour them to the person and situation.