A good friend is honest. They do not speak bad behind you. A good friend tells you the truth even if it hurts you. A good friend does not share your secrets to anyone else. And most importantly, you can trust them. Even if you get caught in a bank robbery, they are still your friends. A good friend is there to help you. They listen to you. I think that listening is the most important part of the friendship. I do not, however, mean that one should speak with friends during a lecture.
I have had maybe four good friends during my life. All of them are in my current class so we see each other often. We have always something to talk about, since we have the same hobbies. If we do not have anything to say about them, we speak about our lives and such. I think that true friend helps one to avoid problems. I base this on the fact that I myself have helped my friends several times, when they have run into trouble. Friends make life worth living. Without friends one is like a lonely island in a big ocean.