It's one of the simplest things you can do. Your mother told you to always say it. By expressing it -- or not -- you can change a person's mood and perception of you in an instant. Who knew two words could be so powerful?

Writing a thank-you letter after an interview doesn't just showcase a candidate's manners - it can also make or break their chances of landing a job. Nearly 15 percent of hiring managers say they would not hire someone who failed to send a thank-you letter after the interview. Thirty-two percent say they would still consider the candidate, but would think less of him or her, according to CareerBuilder.com's "How to Get in the Front Door" survey.

Although most hiring managers expect to receive a thank-you note, format preferences differ. One-in-four hiring managers prefer to receive a thank-you note in e-mail form only; 19 percent want the e-mail followed up with a hard copy; 21 percent want a typed hard copy only and 23 percent prefer just a handwritten note.

No matter which format you choose, it's crucial to act quickly when sending a thank-you letter to your interviewer. Twenty-six percent of hiring managers expect to have the letter in-hand two days after the interview, and 36 percent expect to have it within three to five days. Sending the letter quickly reinforces your enthusiasm for the job, and helps keep you top-of-mind for the interviewer.

Here are some tips to make the most of your thank-you letter:

Stick to three paragraphs.
In the first paragraph, thank the interviewer for the opportunity. Use the second to sell yourself by reminding the hiring manager of your qualifications. In the third paragraph, reiterate your interest in the position.

Fill in the blanks.
Thank-you notes are a great way to add in key information you forgot in the interview, clarify any points or try to ease any reservations the interviewer might have expressed.

Proofread carefully.
Double-check to be sure your note is free from typos and grammatical errors. Don't rely solely on your spell-checker.

Be specific.
Don't send out a generic correspondence. Instead, tailor your note to the specific job and the relationship you have established with the hiring manager.

Survey MethodologyThe CareerBuilder.com survey, "How to Get in the Front Door," was conducted from May 17 to May 27, 2005. Methodology used to collect survey responses totaling more than 650 hiring managers for this study involved selecting a random sample of comScore Networks panel members. These Web Panel members were approached via an e-mail invitation, which asked them to participate in a short online survey. The results of this survey are statistically accurate to within 3.84 percentage points (19 times out of 20).

Rosemary Haefner is CareerBuilder.com?s Vice President of Human Resources and Senior Career Adviser. She is an expert in recruitment trends and tactics, job seeker behavior, workplace issues, employee attitudes and HR initiatives.