If you hang out with bad people, chances are you are also a bad person. If you aren't, you are likely to become one.
Our friends influence us. If you have friends that are great people, chances are they will make you a better person. Choose friends that reflect the person you want to be.
You should also chose the books you read, and the music you listen to with the same criteria. Positive books and music, and you will more likely be a positive person. Works the other way too.
So what kind of person do you want to be?