Once you've created a brilliant cover-letter and resume package, the next step to securing a new position is impressing interviewers. Meeting with hiring managers is stressful, but you can improve your chances of scoring well by avoiding common, yet costly, interview mistakes.

Surprisingly, many job hunters persist in sabotaging interviews. These candidates spend hours on their resume but only a few minutes practicing for interviews. No matter how outstanding your professional experience is, hiring managers won't be impressed if you can't describe it to them.

Not preparing well is a common trait among senior-level executives, who sometimes think interviews are just a formality and attempt to slide through the discussions, says J. Anthony McClure, a partner with Prestige Marketing International, a recruiting firm in Dallas.

"Candidates think the interviewer won't call them on it because they're at such a high-level, but [they] will," he says. Even if a low-key meeting is scheduled, prepare anyway, and you'll appear especially apt for the role.

Arriving on time for interviews may seem too basic to mention, but human resource executives say being late is a frequent mistake that can nix your chances.

"If you can't be on time for an interview, how can you be on time for work?" asks Catherine Godwin, a business manager in Dallas for Lee Hecht Harrison Inc., an outplacement firm based in New York.

Once you're at the office, treat everyone you encounter with respect.

"Never insult or criticize the secretary," says Randy McClarren, a corporate trainer with The Millers Group, an insurance company in Fort Worth, Texas. "When going in for an interview, be pleasant to everyone as soon as you walk in the door because that's when the judging starts."

HR and other employment experts say the following five mistakes are the most common. Avoiding these errors won't guarantee that you'll click with hiring managers, but it can increase your chances of making it to the second round.

1. Dressing unprofessionally.

Interviews allow hiring managers to put a face with a resume. Your appearance is the first thing they'll see, so dress professionally when meeting with company representatives.

"You don't have to look like you stepped out of Vogue magazine, but you should appear neat and kempt," says Vanessa G. Partin, human resources manager for Kirkland & Ellis law firm in Washington, D.C.

A simple, traditional business outfit is always a safe and appropriate choice. Tailored suits are best for men and women, unless the company's work environment or your field dictates otherwise. Don't drape yourself in flashy jewelry, wear loud prints or use cologne heavily. And even if your meeting is on a Friday, when the firm's employees dress down, never wear casual attire.

"If you want to work in an office environment, you need to put forth a professional image," says Jo Hasse, assistant director of personnel for EMS, Inc., a para-medical occupational health-testing company in Dallas. "Once, a candidate came to an interview wearing blue jeans. This was wrong."

2. Arriving unprepared.

An interview is an opportunity to sell yourself and your skills to a hiring manager, so be prepared for every meeting. If you don't know what products or services a company sells or what position you're interviewing for, you won't seem interested.

"It helps to know the company and to have done background research," says William Fierke, director of human resources for Wenger Corp., a manufacturing company in Owatanna, Minn. "This shows you're truly interested in the job."

Before you arrive, determine your career goals and what the available job can offer so you can discuss both these topics with employers, says Anthony D. Shaddix, national field operations manager of Brinks Home Security Inc. in Carrollton, Texas. "Candidates need to have a career direction," he says.

Preparation also means assembling the materials you'll need for a successful presentation. "You should always have an extra copy of your resume to give to the interviewer," says Mr. McClarren. "Also have the names, addresses and phone numbers of references, in case you have to complete a job application form."

3. Discussing compensation too soon.

You may be curious about how much you'd earn, but resist the urge to ask about it during the first interview. If you mention compensation, you'll appear more concerned with personal gain than what you can contribute, and you probably won't be asked back for a second meeting.

Employers want to know what you can add to the company. If you have the right experience and background, you'll receive an offer and the opportunity to negotiate a competitive package.

"It's a huge mistake when candidates want to know instantly what the salary is," says Mr. Shaddix. To negotiate well, research is critical, he adds. "If the company says it pays a competitive range for the industry, then you should know what that range is," he says.

4. Acting desperate.

If you've been job hunting for a while and feel pressure financially, you may leap to accept the first position you're offered. But desperation is the kiss of death during interviews.

If candidates seem ready to accept anything, they won't be desirable to interviewers, says Mr. McClarren. Always know what you want and be sure the positions you apply for meet these requirements.

Never say "I know I'm overqualified" or "I know I'm too old," says Mary Cheddie, vice president of human resources for Gables Residential Trust, a real-estate investment trust based in Irving, Texas. If you've been invited to interview, the company has reviewed your resume and knows your qualifications, experience and approximate age, she says.

When meeting employers, strive to appear calm, self-confident and in control. Say that you're challenged most by the career opportunity and make money a secondary concern.

Don't oversell yourself or try too hard, says Ms. Cheddie. It's up to the interviewer to interest you in a role, she adds.

"The company wants to get you excited about the position," she says. "They don't want someone who's desperate and willing to do anything."

5. Appearing too nervous.

Aim to establish good rapport with hiring managers and express your accomplishments articulately. Ask questions during the meeting, and take notes about the available position, job responsibilities and company, says Ms. Partin. Note-taking helps you follow the conversation and remember issues that were previously discussed.

Show alertness by sitting forward and making eye contact. Eliminate nervous habits, such as jiggling in your seat, playing with your hair or tapping your foot.

"Of course, you're nervous," says Ms. Partin. "The interviewer understands that, but control your emotions." To calm jitters, she recommends holding a pen.

Interviews shouldn't intimidate you. Instead, view them as opportunities to boast about your experience. By preparing thoroughly, you'll avoid making common interview mistakes and pass initial screenings with flying colors.

--Ms. Rurak is a staff writer for the National Business Employment Weekly.