Don't be one to say, "If I could only do it over", after your next job interview. It's not uncommon to lose sleep over an upcoming interview or to fret over your performance afterwards. It's something else though, to lose a shot at a great opportunity after you realize you made a dumb mistake you could have avoided.

Avoid these five common interviewing mistakes that can make you look dumb and eliminate you from further consideration.

1. Not Doing Your Research
This is one of the most common complaints hiring managers make today. By not conducting research beforehand, you lack basic knowledge about the company and the job opportunity. You look foolish and you'll likely be rejected because you've given the strong message that you don't care enough about the company or the opportunity.

Before your interview, find out:
How large is the company?
What products/services do they offer?
Who are their competitors?
Where do they rank in their market?
What is their financial situation?

Knowing as much information as possible up front puts you in a power position when you interview. You're now prepared to talk intelligently about the company, the opportunity and the company's products, and to use this information to engage in a knowledgeable conversation with your interviewer.

2. Being Needy
Neediness could be the number-one advantage-killer in an interview. Even if you have the car payment due and the rent to pay, don't project yourself as needy. Employers can sense desperation and it's a major turn-off. Neediness negates any advantage you hold with your strong skills and achievements. Remind yourself before walking in the door: you need food, air, and water. You do NOT need this particular job. Keep things in perspective.

3. Getting Emotional
At times the interviewer may hit a nerve. He or she may even consciously try to provoke you into an "outburst." Don't fall for it. Before you walk into the interview room, clear your mind of any fears, anger, smoldering resentments or other negativity. Perhaps you just had a disagreement with your partner, your dog may have died, or a close relative was just diagnosed with cancer. Life happens. Put it all aside for the next hour so you can maintain a calm, open-minded presence with your interviewer. When negative emotions enter into an interview, failure follows.

4. Not Asking Questions
Tattoo this on your forehead: You're here to interview them. Your objective is to discover whether this organization is a good fit for YOU. Too many candidates treat the interview as an interrogation when it should be a conversation. Don't just answer their questions. You want to find out more about what this job is really about and whether you want it.

Arrive with a list of prepared questions about the company, the position, and the people who work there. Ask questions that begin with "what," "how," and "why." Avoid simple yes/no questions. Get your interviewer talking as much as possible, and then take notes. Most interviewers are unimpressed by candidates who have no questions, as it shows a lack of interest or initiative.

5. Not Closing
There is one important question most candidates don't ask at all. This is the closing question at the end of the interview. You need to know what happens after this interview. Many books advise asking for the job here, but you may feel intimidated to bluntly do so. With other candidates scheduled to interview, the hiring manager is not likely to make you an offer yet. You may need to do some additional research on the company, making it too early to ask for the job.

A good compromise is to let them know you're interested in the job. Then, ask this question, "What's our next step?" This way, you won't be left with any surprises. Remember to ask for the interviewer's direct phone number and the best time to call to follow up.

Summary

A successful performance at your interview can make all the difference in winning that job offer. You can get there a lot faster by avoiding these five common interviewing mistakes that not only make you look dumb, but also lose a good opportunity.