First impressions are crucial. We rely on them and in 2006 psychologists found we can make reliable judgments of strangers in a tenth of a second. That’s faster than the blink of an eye. More importantly, these impressions dye the memory and become hard to change. The brain returns to them again and again.

And how do you make your first impression with an employer?

Answer: With your cover letter.

That’s right. With that letter you may have hastily composed to explain the obvious: That you’ve attached a resume.

Don't let the name fool you. “Cover letter” suggests afterthought, slap-on status. Yet it is critical, since:

1. It speaks for you before the resume. It introduces you. A pleasant, clear, brief cover letter conveys one message; a remote, gnarled, wandering letter another.

2. It highlights aspects of your career that might otherwise get lost in the resume. It gives you a chance to aim spotlights at the right places.

3. It shows your care for detail. Or, rather, it shows that you aren’t careless, that you haven’t dashed off a last-minute message.

4. It can reveal your judgment. For instance, if you mention irrelevancies like hobbies in the cover letter, you can trip yourself up. No one wants an executive with poor judgment.

5. It’s you. The resume is data, presumably well-polished, but the cover letter is your voice. It’s the prelude to the interview. You stand on the foundation of the resume, which indicates what you can do. The cover letter suggests how you will do it.

For all these reasons, employers often scrutinize the cover letter. Countless smart executives have never heard back because their cover letters sabotaged them. On the other hand, a sharp one helps move you to the top of the resume stack. Take the time to make sure you get the cover letter right. Just as you pay attention to that firm handshake.