If you've ever hired someone only to realize later that doing so was a huge mistake, you know how expensive, time-consuming, awkward, productivity-killing, and growth-hindering it is. On the flip side, bring the perfect person on board and you can get more work done, help your team jell, and catapult your company into unexpected success.

Tom Gimbel, founder, president, and CEO of the Chicago-based staffing company LaSalle Network, has some ideas on how you can find that perfect person every time.

Always be interviewing.

Ideally, you have a fantastic team and no one ever leaves. Even if that's really the case, you should proactively keep your hand in the talent pool so you can accommodate growth.

Ask yourself: If you got an influx of new business, which areas of the company would be overwhelmed? Is your delivery team knocking the cover off the ball? If so, you might need more salespeople somewhere down the line. Even if you just hired someone and you have a gut feeling it might not be a good fit, start talking to candidates right away.

"The key is to do an evaluation of your business and say, 'Where are we strong? Where are we weak?'" Gimbel says. "If you know where you're weak you should be interviewing in those places anyway. You shouldn't be waiting to fire. You don't want to start interviewing after you fire somebody. Too often I see entrepreneurs and business leaders fire somebody and then...need to replace them. That's ridiculous. I mean, I get it, and sometimes things come out of the blue, but you should always be looking."

Take your time with the interview process.

When you do identify a candidate who looks promising, have them meet a lot of people within your company.

"I think to hire somebody on one interview is crazy," Gimbel says. "You need to vet people out and gauge their interest. I also think it shows the professionalism of your company that you give them the courtesy of coming back to meet other people. You get a lot of growing companies that say 'We need you. Here's an offer right now.' And it really it throws some people off."

Fire quickly.

It might be common sense to quickly get rid of people who aren't a good fit, but firing is usually a painful process for everyone involved and--human nature being what it is--people will put off doing uncomfortable things.

"Especially in smaller, growing companies, the wrong hire is a cancer and you have to get rid of it," Gimbel says. "Especially an attitude [problem]. If you have a high-performing group that's working a ton of hours and you put in a poor performer, all you're doing is weakening the entire machine. You have to be ready to get rid of those people fast and show your other staff members that you're a leader of strength."

Make sure you like the person.

This might sound like a no-brainer but when you're faced with the opportunity to hire some kind of genius or a person with stellar technical skills it can be easy to overlook the reality that he or she might bug the heck out of you or other people on an interpersonal level.

"You need to want to spend time with the people who are on your team, especially in a fast-paced, high-growth company," Gimbel says. "If you think sitting on an airplane for four hours with this person would drive you crazy, then don't hire them."

Don't necessarily cast off the candidate who's missing one critical skill.

Imagine you're hiring for a position in which the person will need to create reports in Excel. You find someone who's seemingly perfect in many ways. She has a great attitude, a top-notch education, and great experience, but alas, she doesn't know how to create a spreadsheet.

Maybe you should shell out the $500 it might cost to get her trained in Excel.

"Now I'm not saying you can take somebody who can't turn on a computer and turn him into the best coder in the world, but I am saying sometimes you just have to think outside the box and say, 'This person really has got the attitude and the work ethic and some experiences that can really help us. How can we fast-forward them on some other areas to be what we need them to be?'" Gimbel says.

Hire according to your core values.

It sounds cliché, but if you know what attitudes and behaviors are important to you, it's easy to filter candidates accordingly.

Maybe your company doesn't care if somebody shows up for work unshaven, wearing jeans, and with messy hair but prioritizes manners and respectful behavior.

"If [a candidate] is in a conference room, I'll have somebody go in there 'accidentally,' shake their hand, and see how the person interacts with someone who's not part of the interview," Gimbel says.

Be a skeptic.

If you need whomever you hire to lead a difficult software conversion or drive massive growth, it's easy to go into an interview and use leading questions that may tempt people to overstate their experience.

"You should go in skeptical, and that person should prove you wrong," Gimbel says. "Most people go into interviews wanting to like the person and have them be the perfect fit. You should go in planning on being disappointed, and hopefully be pleasantly surprised."