Use This Green Beret Method to Find Out if Someone Is Trustworthy Thinking about a new partnership? Check these boxes before you sign on the dotted line.

In our ongoing psychological warfare series, former Green Beret Sergeant Major (retired) Karl Erickson has shared simple methods you can use to tell if someone is lying, as well as a couple of tricks to get a liar to tell the truth.

This week, he turns his attention to partnerships. While commanding special forces missions over the past decades, Erickson had to quickly learn how to find reliable partners that wanted to help him succeed, and avoid bad partners that wanted him to die.

While life and death (hopefully) isn't factoring into your business relationships, here are some of his tips to see if you're signing up for a fruitful or frightful partnership.

Know your enemy.

"Or in this case, know your potential new partner. The first thing I'd advise you to do is to do your research prior to your initial meeting. Gauge their past performance. Did they have success? Were those successes one-sided or did both partners do well? Meaning, did he or she make money for everyone or just for themselves? Ask around and find out. Forget resumes, everyone flowers them up and makes it seem like they single-handedly parted the Red Sea. Talk to people who have done business with them before. So many say that this person screwed them over, but did everyone say the same thing?"

Related: How to Tell if Someone Is Lying

Realize that people can change.

"Talk to people, but understand that you can't always go off of past relationships. Just because one guy says I knew that guy back in college and he is a piece of shit doesn't mean he still is. Most psychologists say that your values are established by the time you are 12 years old, developed by your environment and experience. But I have seen that time and education can change a person. I've dealt with new guys in special forces who were too cocky and were just terrible to work with. Then you fast forward 15 years and the guy is in a much higher leadership position, making larger-scale strategic decisions and you realize that people can mature. So don't base everything on one person's negative experience."

They should distrust you.

"In Afghanistan, the Army would roll into a village and tell the tribal leader, 'We have money for you, we're going to build you a well, we're here to help. We just need you to tell us where the bad guys are.' And they'd get the stink eye. And they'd get labeled as 'hostile.' But then the Special Forces guys went in, and besides being much better looking, realized that that isn't how the culture functioned. They'd accept an offer of tea from the tribal leader, and just have a pleasant, informal chat. It might take three meetings like this, but, eventually, the leader felt that trust was earned and they could talk business.

"So a person who is keeping you at arm's length at first shows that they are skeptical and are thoughtful. That's good! If someone is 'yes, yes, yes,' you need to wonder why they are so willing to help. They're either dumb or see an opportunity to take you for a ride, neither of which is what you want. I want a partner who is as suspicious of me as I am of him. I'm looking for a long-term trustworthy partner and I want him to be looking for the same thing."

Related: 7 Trust-Building Tips To Use In Your Business

Look for we vs. me.

"An 'A-team' is the 12-man team that Army Special Forces is built on. You have to trust the guys to your left and right with your life. I believe in the idea of 'One Team, One Fight.' Is he willing to work to benefit all partners or just himself? One simple way to know that is just by listening to the person talk about their company. Do they say "I did this" or does they say "we did this"? That's a good indicator."

Related: 11 Ways to Make Money While You Sleep

Can they embrace the gray area?

"You want to work with someone who understands the black and white of legal issues -- but understands that to get things done, sometimes you need to operate in the gray area. For example, when I was in Fallujah in 2004, I needed a crane to fix this safe house we were in. I had an operations fund, but I couldn't take the taxpayers money to buy a crane. The money was only to be used for food and things like that. So I took some of that opfund money and bought some steaks, some alcohol and I invited two Marine generals and the heads of a security contractor company for dinner. We relaxed, talked informally, and by the end of it, they said, 'Karl, if you ever need anything, you just let us know.' And I said, 'Well, as a matter of fact, I need a crane tomorrow morning.' And at 8 the next morning, I had a crane and an operator parked right outside my gate. I didn't break any laws, but I operated in that gray area to get what needed to be done. That's what I want in a partner.

"So in conversing with a potential new partner, I'll talk about what is going in the news and pose a few hypotheticals. 'If we could get away with it, we should do this.' See how they react. There are a lot of companies who are willing to eagerly cross the line and hope they don't get caught. I can't do that."

Trust your gut.

"Everything can seem perfect on paper, but if something doesn't seem right, just walk away. I can't tell you how many times on a convey that the lead vehicle will stop and the driver will say, 'Something doesn't feel right.' Even though there is nothing in particular to point out as wrong, we'll divert the convoy and go another route. And time and time again, you'll learn afterward that there was an IED or an ambush waiting. Don't overthink it and don't override your instincts. If something feels wrong, it probably is."

Erickson tests tactical gear on his site Tactical Rifleman. Follow him at @TacRifleman.