(CareerBuilder.com) -- Over the years, hiring managers have born witness to every hiring, interviewing, résumé, cover letter and negotiation mistake there is.
You know what these blunders are. Yet you (and hundreds of other job seekers) continue to make common job search mistakes.
From those who see your mistakes over and over, here are 16 common job search mistakes to avoid -- and some of them may surprise you.
1. You don't keep your options open
"Candidates tend to think that if they interview for a job they will get an offer, so they do not apply and interview for multiple positions," says Joanie Spain, director of public relations and career services, School of Advertising Art, a graphic design college. "They wait until one plays out completely, putting their job search on hold until knowing for sure they didn't get the offer."
"By having many more irons in the fire, you diversify the risk and disappointment that is inevitable when any single opportunity disappears," adds Roy Cohen, author of "The Wall Street Professional's Survival Guide: Success Secrets of a Career Coach."
"You also present yourself as a more passionate and energetic candidate. You're in the 'zone' -- a point where you're in the flow of information and ideas -- and that makes you more valuable."
2. You turn up your nose at job descriptions
"Entry-level candidates are reluctant to apply for a position unless the job sounds like their 'dream job' or they have all qualifications listed," Spain says.
"Rather than going on an interview to get more information, they base decisions about applying on the job description alone. They fail to see that all interview experience is good experience, or that, until there is an offer on the table, there is no decision to make."
3. You haven't perfected the thank-you note
"Don't be too verbose with a thank-you note after an interview. Sending out a version of "War and Peace" can come across as desperate and needy for a job. However, sending a one or two sentence thank-you note comes across as flippant, not well thought-out and potentially shows indifference regarding the job to the employer," says Mike Barefoot, senior account manager at Red Zone Resources, a recruitment firm.
"We encourage candidates to keep them to four to eight sentences."
4. You don't check your references
"Always give out references that you've pre-screened. We sometimes see candidates give out references that were never checked with and the references feedback isn't always kind," Barefoot says.
"Also, make sure they're predominantly managers. An occasional colleague is okay, but contemporaries and friends really don't carry that much weight in helping you land a position."
5. You've got poor business acumen
"Managers are becoming more savvy and are taking candidates out to lunch for interviews. They want to see how you treat a restaurant staff and see the 'real' you. If you're rude to them or don't seem appreciative for their hard work to make your meal pleasurable, managers wonder how you'll treat contemporaries you work with," Barefoot says.
6. You have a messy briefcase
"A messy briefcase can imply the person is unorganized, messy and unprepared, and that their work will be less than optimal," says Ronald Kaufman, author of "Anatomy of Success."
"Someone who is neat, clean, organized and prepared in all areas conveys they're serious about getting a job and working."
7. You discount temporary positions
"Many employers coming out of a recession want to hire on a temporary or temp- to perm- basis. We have already seen several contractors be offered permanent positions after they have proven themselves," says Jeffrey Weinstock, Esq. president, Rhodes & Weinstock, a recruiting firm.
"Not only will the temporary position pay some bills, think of it as an audition for a potential perm position, or at least a way to get a good reference for another position."
8. You have a bad attitude
"Poor attitudes come through in telephone calls and in interviews. If you are not positive, why would a potential employer want to hire you?" asks Weinstock. "It may take some time, but by being positive, by doing all the right things, by seeing each position as an opportunity, it will happen."
9. You include too much work history
"Many job seekers over 40 think that they have to take their work history back to their first job out of college," says Cheryl E. Palmer, career coach and résumé writer. " All that is needed is the last 10-15 years of your work history."
10. You use your work email address on your résumé
"Some people do not regularly check their personal email, so they use their employers' email instead," Palmer says. "This sends a negative message to potential employers that the job seekers will not hesitate to use their equipment for personal use."
11. You take "no" as a final answer
"No" usually only means "no" for that position, says Bruce Hurwitz, president and CEO, Hurwitz Strategic Staffing, LTD.
"If you are rejected for a job you should send a thank-you note, thank the employer for the opportunity, and wish them well. No one does that. When the next opening comes around, he'll remember you," says Hurwitz.
12. You lack tact
"Be determined without being pushy. Calling or emailing to ask about the status of your résumé or interview can be a double-edged sword," says Rod Hughes, director of communications, Oxford Communications.
"A tactful follow up can place you top of mind with the hiring manager, while incessant calling or emailing can push your résumé right off the table."
13. You don't search for yourself on the Internet
"Your would-be employer is probably going to look you up online, so you should know what is out there," says Amanda O'Brien, vice president of marketing, Hall Web Services.
"Clean up what you can, check your privacy settings on social networks and if it is something you can't get down off the internet, you may want to consider talking to the company about it."
14. You have a 'death by bullets' résumé
"Bullets are great but they need context. Keep them to one line, focused on a result and include a figure like a fact, percentage or number," says Adriana Llames, author of "Career Sudoku: 9 Ways to Win the Job Search Game." "Or, put the information in a short summary of the position."
15. You've got a scattered strategy
"Looking for a job in any industry and with two or three résumés is going to get the same result as the strategy: scattered," Llames says. "Job seekers with a clearly defined, focused and organized strategic approach to their job search end up with clear results -- and a new job."
16. You think it's about you
It is not about you and your need for a job -- it is about the prospective employer and their need to run a successful business and make money, says Lori B. Rassas, employment attorney and author of "Employment Law: A Guide to Hiring, Managing and Firing for Employers and Employees."
"Many applicants mistakenly believe they will be an appealing candidate if they explain they will accept any type of job offer at any salary because they have been laid off, unemployed for an extended period of time, have children in college, or are having difficulty making the mortgage payments," she says.
"Even if all of those circumstances are true, candidates need to craft a different message, focusing on how they can benefit the employer by saving them money, streamlining processes, creating additional sources of revenue and bringing overall value to the company."
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