Here's the thing about snap judgments: They seem unfair, but we all make them. Why? Because they're usually pretty accurate.

Harvard research has shown that students who viewed a silent video clip of a professor teaching for just two seconds rated that professor's performance nearly as well as students who had spent a whole semester in the professor's class. Our body language really does give away our character -- and it does so really, really fast.

First impressions also color the whole rest of the relationship. As Nicholas Boothman, speaker and author of How to Make People Like You in 90 Seconds or Less, explained in one of his talks, "when you like someone you see the best in them. If I like the guy, he's enthusiastic. If I don't like him, he's overbearing. If I like her, she's kind. If I don't like her, she's weak."

But here's another thing to keep in mind -- changing your body language is simple. In fact, according to Boothman, doing three incredibly straightforward things within the first two seconds of meeting someone can make you instantly likable to nearly everyone. Here they are:

1. Look them in the eyes.

Some people struggle with eye contact. If you're one of them, here's an easy hack to get over your shyness: "When you meet someone for the first time, just notice what color their eyes are. That'll do it," suggests Boothman.

2. Smile.

Step two couldn't be simpler, and as Business Insider pointed out in its write-up of Boothman's book, "research also suggests that smiling when you meet someone in a happy context is a useful way to get them to remember you."

3. Open your body language.

This one takes a bit more explaining, but once you know what "open your body language" means, accomplishing it is as simple as the first two steps. To win trust and make people like you, ensure that when you meet them, you aim your heart directly at them. No crossed arms. No buttoned-up suit jacket. Make sure there's nothing between your chest and theirs but that winning smile of yours.