When we meet someone for the first time, some of the first things we notice is their face, clothes, and hair. Basically, how they present themselves. It's normal for us to make judgments based on what we think we know about a person from the second we lay eyes on them. To put it short, we judge what we don't know. Each and every individual person has a unique story, obstacles, and experiences that they have faced in their lives that play a role in how we shape our personalities and what we identify with. We never truly understand a person until we hear their story.
Many people have different opinions on whether their first impressions of other people are accurate or not. I asked around, and many of my current friends had somewhat accurate first impressions of me, and many of them thought that the first impressions that they have of others are generally correct, but it varies with everyone.
Personally, more often than not, I find that some people end up being the opposite of the first impressions that I have of them. The people who I initially perceive as very sweet and nice, turn out being more fake towards me. And the people who are more blunt and straightforward with their opinions, tend to be the people I grow close with. This is not always true, but you never know an individual's true colors until you are in a stressful situation with that person. The way that a person treats you when you are on bad terms with them plays a big role when making the judgment if someone is a good person or not.
What's important is that we keep an open mind when meeting people for the first time. It usually takes a deep conversation or two to have somewhat more of an idea of a person's experiences. We tend to grow closer with people by connecting with our experiences and dealing through situations with them.