It takes time to get to know someone.  If you like the person immediately and they seem to like you, then spend time talking and getting to know how they feel about certain things that are important to you.  Watch how they treat others.  If they gossip and whisper to you about other people, they will do the same about you to others.  Treat others the way you want to be treated and hang around with the ones who are kind and decent to you.