Everyone's got a story about how they thought a certain friend was mean the first time they met, but realized later that he or she is actually the nicest person ever.
Generally, you've only got a few seconds to make someone want to spend more time with you. Everything matters — from your last name to the smell of your sweat (gross, we know).
Below, Business Insider rounded up various scientific findings on the traits and behaviors that make people dislike you, both online and in person.
1. Sharing too many photos on Facebook
If you're the kind of person who shares snapshots of your honeymoon, cousin's graduation, and dog dressed in a Halloween costume all in the same day, you might want to stop.
A 2013 study found that posting too many photos on Facebook can hurt your real-life relationships.
"This is because people, other than very close friends and relatives, don't seem to relate well to those who constantly share photos of themselves," lead study author David Houghton, of Birmingham Business School, said in a release.
Specifically, friends don't like it when you've got too many photos of family, and relatives don't like it when you've got too many photos of friends.
Ben Marder, of the University of Edinburgh, also worked on the study, and warned: "Be cautious when sharing and think how it will be perceived by all the others who may see it. Although sharing is a great way to better relationships, it can also damage them."
2. Having too many, or too few, Facebook friends
In a 2008 study, Michigan State University researchers asked college students to look at fictional Facebook profiles and decide how much they liked the profiles' owners.
Results showed that the "sweet spot" for likability was about 300 friends. Likability ratings were lowest when a profile owner had only about 100 friends, and almost as low when they had more than 300 friends.
As for why 300-plus friends could be a turn-off, the study authors write, "Individuals with too many friends may appear to be focusing too much on Facebook, friending out of desperation rather than popularity."
On the other hand, the college students doing the evaluation each had about 300 Facebook friends themselves. So the researchers acknowledge that in a population where the most common number of Facebook friends is 1,000, the sweet spot for likability could be 1,000.
Keep in mind, though, that a 2014 survey found that the average number of Facebook friends among adult users was 338.
Interestingly, the study also suggested that participants weren't consciously aware that they liked people less when they had too many or too few Facebook friends.