I think I've gotten much better with meeting new people since my awkward preteen years where new things of any kind would terrorize me, but I think I still have a lot to learn when it comes to embracing different ideas. Going to college was the first time I had ever been in a situation where I didn't know one soul, and it was the most frightening thing I had ever done. As someone who is much more shy than outgoing, especially in new situations, it felt incredibly brave. It taught me to talk to others, ask questions, form connections with people, even if temporary, and it made me think about how I portray myself to others. This is something you don't often think about in high school when you have known the students in your class for twelve years and assume that everyone already knows you. When I meet new people, I immediately start wondering if the personalities they portray while I'm talking to them coincide with their regular, everyday personalities with people they're comfortable with. Are they rambling and going off on tangents because they're nervous like me, or do they generally talk a lot? And how do I judge that person based on this one interaction?
I have found that 99% of the time, I shouldn't base my judgements of people on my first impressions of them. Not only do many people act differently when first meeting others, but it's important to remember that not everyone is at their best all of the time. Maybe the dining hall staff member snaps at you for accidentally cutting in line, and you decide that you don't like her because of this interaction. She could just have a tendency to be rude, but what people often don't realize is that, maybe, just before you walked in, three other people blatantly cut in line and then disregarded her more polite admonishment. If someone acts differently than how you think it's acceptable to act, don't write them off just yet. Put yourself in their shoes and give them another chance.
Alternatively, sometimes I find myself being intimidated by how perfect a person seems. When I meet someone who appears confident, friendly, funny, and just the right amount of quirky, I find myself envying their social expertise. But perhaps they aren't actually as confident as they seem; maybe they are seriously struggling in school or have a really hard home life they are trying to compensate for with their social life. I have learned to remind myself that nobody, no matter how they appear, is perfect. Everyone has hardships and faults that they struggle with, so don't let yourself think that anybody's life is flawless.
Give people the benefit of the doubt and remember that people might be acting based on circumstantial factors, not personality traits. It's important to keep in mind each individual person's story and how it affects them, and to give people second chances. Your first impression of someone can be very different from your overall impression of that person after getting to know them. Being mindful of others' experiences that might be unknown to you and the reasons for their actions can lead to less negative thoughts and a more accepting attitude.