How you conduct yourself before an interview begins is just as important as the interview itself, says HR expert Barry Drexler.
Drexler, who has over 30 years of HR experience, tells CNBC Make It that an interview starts before you've even stepped foot in the building so it's imperative that you're on your best behavior.
"Don't let your guard down within 10 miles [of the interview location]," advises Dexler. "You go to the coffee shop, how do you know who you're going to run into there?"
While this may sound like common sense, Drexler explains that many applicants don't take this into consideration when heading into an interview. "It's all about first impressions," he says.
To help you avoid tanking an interview before it's even begun, here are the six most common mistakes applicants make, according to Drexler:
1. Looking at your phone or reading
Body language is extremely important when it comes to making a good first impression, says Drexler. "You want to have a comfortable open stance with shoulders back," he says.
Yet many applicants sit in the waiting room prior to an interview and "hunch over" as they scroll through their phones or read a magazine. Even worse, they sometimes hold phone conversations.
"Picture this," says Drexler, "I come out and you're fumbling with a magazine. Now your first impression is gone. Or you're on your phone and I have my hand out but you're fiddling with your phone. That first impression is gone."
In fact, Drexler says that phones have no place in the waiting area and he advises people to simply turn them off. That way, you aren't tempted to check your Twitter feed and you don't run the risk of your phone ringing during the interview.
"I swear, you can't imagine how many times people's phones go off. It's awful," says Drexler. "That's like amateur hour. Make sure it's freaking off. It drives me crazy."
Also, refrain from reading, says Drexler. Instead, he says to "sit strong or stand."
2. Giving clammy or weak handshakes
You'd think giving a proper handshake would be the easiest part of the interview process but many candidates don't give a proper strong handshake, according to Drexler.
"I'd say half the people really have to work on that," he says. "Some are wet and clammy. It's terrible. First impression gone."
Science backs up the power of a firm handshake. According to Psychology Today, a study found that applicants with firm handshakes had higher hiring potential and were viewed much more favorably than others. Participants with firm handshakes were also described as "more positive and outgoing and less socially anxious."
3. Appearing disheveled and poorly dressed
It's always better to be overdressed than underdressed, says Drexler. Even in casual settings, like the tech industry, Drexler says that you should never show up to an interview in casual clothing. "It doesn't work that way," he says. "Wear a suit and tie and, if you feel overdressed, you can always take your jacket off."
Additionally, don't wear anything distracting, whether it's clothing or jewelry. "You want people to notice you in your clothes, not your clothes," says the HR expert.
As for shoes, make sure that they're polished and never wear sneakers. "I've had people show up in sneakers," says Drexler. "I had to ask the receptionist..., 'Did this person really just show up in sneakers?'"
Once you arrive at your interview location, give yourself a final look-over, he says.
4. Unable to make small talk
"Small talk is a skill. Learn it," says Drexler. Typically, when you arrive at an interview, the hiring manager comes to collect you and escorts you to an office or private space. As you walk, smile at your interviewer, he says. Don't act nervous and make sure you have a positive upbeat personality.
Once you arrive at the area where the interview will take place, feel free to remark on the space. For example, "You have a beautiful office" or "Are those your kids in that photo on your desk? They're adorable."
"Be a nice person," says Drexler. "Be open and warm."
5. Wearing too much cologne or perfume
Your interviewer shouldn't be able to smell you before they see you. In fact, Drexler advises that you don't wear any cologne or perfume.
"I've had women show up with perfume that's so overpowering that I had to leave my office after the interview and let it air out," he says. "And then that becomes the only thing that you remember."
Another reason to avoid wearing any perfume or cologne is because a person's sense of smell is closely linked to memory. A scent can remind your interviewer of a past significant other or someone he or she hated, says Drexler.
Plus everyone's tastes are different, he says, so the interviewer may not like your aroma. "What if I hate your perfume? I'm going to be sitting there suffering," he says. "It's distracting."
Drexler has the same issue with men. "The cologne is so powerful that when I shake their hand their cologne is on me," says Drexler. "And it's cologne that I hate."
He ends with this, "Don't wear perfume or cologne. You don't have to. Don't do it."
6. Behaving rudely in the reception area
Unbeknownst to many, says Drexler, the receptionist and building security can make or break your chance of getting hired.
"The first person I would ask what they thought [about a candidate] was the receptionist and then the security guard," says Drexler. "People don't realize this."
The HR expert says he's heard of applicants waiting in the reception area and behaving rudely to other interviewees or the security guard. "And they don't think it's going to get back to me," he says.
However, that's a big error on their part. After every interview, he makes it a point to ask how interviewees conducted themselves in the reception area. "Because that's when people's guard is down," explains Drexler. "They don't realize someone's watching."
Again, this is why it's crucial to always be aware of your surroundings, says the interview coach. "Be polite and friendly to everybody."
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