One of the world's foremost experts on crime reveals 7 tell-tale signs when someone is trying to con you

Typecasting is a technique con artists generally use to get someone's full attention.

It always involves a slight insult, de Becker writes, that is easy to refute. For example, a man at a bar tells a woman that she's probably too snobbish to talk to him.

She could easily prove him wrong by sparking a conversation, but the best defense against typecasting is to ignore the remark entirely because acknowledging it is exactly what the typecaster wants.

Charm is almost always a tool people use to attain a certain goal, according to de Becker.

Most charmers aren't a threat, but many criminals will use charm to deceive you of their harmful intentions. A helpful way to see around the charmer for who the person truly is, de Becker says to consciously tell yourself:

"'This person is trying to charm me,'" as opposed to, 'This person is charming.'"

Every con, big or small, relies on one thing: distracting you from the obvious. One of the most obvious facts in a questionable situation is when you're approached by a stranger.

De Becker says that often times criminals will converse with their victims a little too much, feeding them too many details about false experiences in order to distract their victims from the obvious fact that the person doesn't know them at all.

Moreover, the reason criminals give too many details is a telling sign of their malintent:

"When people are telling the truth, they don't feel doubted, so they don't feel the need for additional support in the form of details. When people lie, however, even if what they say sounds credible to you, it doesn't sound credible to them, so they keep talking," de Becker writes.

Always be suspicious of a stranger who says "I promise."

Promises are "the very hollow instruments of speech," according to de Becker, because they do nothing more than reveal someone's attempt to convince you of something.

Whenever someone gives you an unsolicited promise, defend yourself by thinking: "You're right, I am hesitant about trusting you, and maybe with good reason. Thank you for pointing it out," De Becker writes.

Loan sharking is a technique con artists use to get you in their debt. They'll do something for you, like help carry groceries to your car, but will expect a greater favor in return.

Most people are not criminals and might simply want to help, de Becker says, but just to be safe listen to your intuition and look out for other signals that suggests this person might not be as generous as they want you to think.

De Becker says that ignoring the word "no" is the most universally significant signal that you should not trust this person.

"Declining to hear 'no' is a signal that someone is either seeking control or refusing to relinquish it," de Becker writes later adding that, "If you let someone talk you out of the word 'no', you might as well wear a sign that reads, 'You are in charge.'"