Sometimes, all it takes is a small mistake or oversight to turn off a potential employer. Calvin Sun offers this list of job-search gaffes that could torpedo your chances of getting hired.

Searching for a job requires you to do a lot of things the right way, avoiding missteps that can doom your efforts despite your strong qualifications and experience. Here are a few simple things to watch out for when your job-hunting campaign is underway.

Note: This information is also available as a PDF download.

#1: Relying on human resources office

You’ve heard it before, certainly, but the advice still remains valid: Don’t send your resume to human resources, or the hiring department, or the hiring manager. In most cases, these departments serve only screen people out. You’re much better off finding the name of a specific person, namely your prospective boss. If that person likes your qualifications, he or she might be able to push you through the human resources bureaucracy. Is it possible that that person may simply forward or refer you to human resources? Sure. But you’ve lost nothing in the attempt.

For details on finding and contacting people within a prospective company, see “Breaking through the wall.”

#2: Using an unprofessional e-mail address

You and your friends might think or are funny or clever addresses. Think, however, how a hiring manager might view them. That person might lack your sense of humor, and his or her reaction might hurt your chances. You’re better off with simply your name plus, if necessary, a numerical suffix.

#3: Having an unprofessional telephone greeting

The same logic applies to your voicemail greeting. All you need say is that you’re unavailable — not that you’re out clubbing or playing Wii. Why give a potential hiring manager a reason to pass you by?

#4: Overlooking misspellings in your cover letter

Back in college, a classmate of mine told me that he was applying for a job with what was then known as Morgan Guaranty. The trouble was, throughout the entire cover letter, he referred to them as “Morgan Guarantee.” Not surprisingly, he didn’t get the job.

Misspellings are never good, but they hurt you the worst if they involve the name of the company or the names of people. Check them out thoroughly before sending a letter. Names can be spelled in different ways, e.g. “Anne/Ann,” “Michelle/Michele,” “Scott/Scot.” Furthermore, as companies merge or become acquired, their names often change accordingly. If in doubt, check the company Web site or simply call the receptionist and explain that you want to confirm a spelling.

Remember that while Word has a spell-checker, it doesn’t have a “what you meant to write-checker.” If you wrote “they’re chances” or “there chances” when you meant to say “their chances,” Word won’t flag your phrase (at least it didn’t for me just now). Make sure of your sentences even if Word says the spelling is okay.

#5: Failing to write a post-interview thank you letter

Contrary to what others may say, writing such a note is not signaling desperation on your part, nor does it constitute groveling. When you travel to a company to interview, you are a guest. The person who invited you had to do many things to prepare, such as reserving a conference room and coordinating peoples’ schedules. Your note shows your appreciation for those efforts and gives you an additional chance to reinforce your strong points. Failing to write a note deprives you of that chance and may mark you as being unprofessional.

#6: Dressing inappropriately for the interview

If you’re interviewing at a bank, dress like a bank person. Forget the t-shirt, shorts, and sandals. Forget the too-high or too-tight skirts and too-low blouses. They’re out of place and will hurt your chances. When in doubt, dress more conservatively. Even better, research how people dress and do likewise.

#7: Omitting accomplishments from your resume

Don’t just list responsibilities on your resume. Talk about your accomplishments, and if you can, quantify them. For example, don’t just say, “Wrote programs in [name of language].” Instead, say “Developed system that reduced order entry processing time by x%.”

#8: Arriving late for an interview without letting someone know

If you’re running way behind, call or text ahead to let the interviewer know you’ll be late. Sure, it’s better to be on time. But if you can’t be, at least the people you’re meeting with can continue with other work while waiting for you. The worst alternative of all is to simply show up late. It smacks of rudeness and unprofessionalism and may hurt your chances.

#9: Bad-mouthing a former employer

Much as you might be tempted, and even if the interviewer asks you, avoid bad-mouthing your former company, co-workers, or boss. All you need say is that while you learned a great deal (a true statement, even if your boss and co-workers were horrible), you felt a need to move on and gain more challenge. Bad-mouthing the old company may mark you as a troublemaker by your prospective employer.

#10: Failing to leverage existing contacts

If you’re looking for a job, you don’t have to do it alone. Think of other people who can help, such as former co-workers, vendors, and especially fellow alumni from high school or college. If you fail to do so, you simply make your own search more difficult and frustrating.

This point illustrates the old saying that “One hand washes the other.” Before you need to leverage your existing contacts, think about how you can help others in their own job searches. When you do, you will feel tremendous satisfaction at having done good for someone. And you’ll make it more likely that those persons will later help you in the same way.