You can learn a lot about a person from their handshake. Or at least, you can make a lot of assumptions about a person based on their handshake. Perhaps you assume a weak handshake is the sign of a weak person, while an aggressive handshake indicates overconfidence. Some researchers believe the handshake originated as a way of checking whether the other person had a knife hidden up his sleeve.

In the modern world, I’m not so sure instant judgments based on handshakes are worth much. But for some people, a handshake is very important, so you better have a good one. Firm but not painful, no longer than a couple pumps, dry hands, good eye contact… you get the idea.

Social conventions like handshakes are important signs of respect in business. The instructions I gave above are good to use in the US, but they’re different depending on where you are. On National Handshake Day, here are some international body language conventions to be aware of while you’re traveling for business:

1. Handshakes

Handshakes are increasingly common around the world, but how you do it matters. In some Asian countries, a hard handshake is considered rude. In Vietnam, you should only shake hands with someone who’s your equal in age or rank. In Thailand, instead of shaking hands, you’re more likely to bow with your hands together and up to your chest. And don’t be surprised if someone from France and many other places pulls you in for a double cheek kiss!

2. Headshakes

This can be confusing. In the US and much of the world, nodding your head up and down means “yes,” and shaking it from side to side means “no.” But in Greece, Bulgaria, and some other countries, the opposite is true. Make sure you know which is which!

3. Thumbs Up

In the US, giving a thumbs up means everything’s ok. In Germany, it represents the number 1. But in Australia, Greece, parts of Italy, and the Middle East, it means, “up yours!” It’s probably best to avoid this indicator, even if the movie was really, really good.

4. OK Sign

In the US, making the OK sign, with your thumb and forefinger forming a circle, and the other fingers stretched out and spread, means “great!” In other countries, it’s a sign of the number 0. Seems innocent, right? In Brazil, Germany, and Russia, it references a particular orifice that’s probably best to avoid discussing. Be careful!

5. The V

In the US, making a V generally means “peace,” or references the number 2. No doubt thanks to Winston Churchill, a V with the palm facing out can mean “peace” or “victory.” But it’s not that simple! In Commonwealth countries and some other places around the world, a V with the palm facing in means something not fit for polite conversation.

6. Wave

Be careful with this one. In the US, putting your hand up with your palm out is a ubiquitous, friendly greeting. In certain contexts, it can also mean, “stop.” But in Greece, Pakistan, and some other countries, this gesture is used to mimic wiping feces over the other person’s face. Make sure you’re sending the greeting you intended!

7. Come Here

In the US, curling your index finger with the palm up means, “come here.” It can be done in a provocative, “come hither” manner, but it’s generally an innocent gesture. This is not so in other places. In parts of Eastern Europe and Asia, it means something very different, and you should avoid it.