How do you know whether someone is your "true" friend?

I've been having difficulties trusting people and developing genuine relationship. Partly due to the betrayals that my past friends did and shitty things that people did to me, I lost faith in human relationship and isolated myself. But I've been trying to overcome my fear and insecurity to develop more genuine relationship. But the question is how do I know whether someone is a good and trustworthy friend? Should I trust my instinct or should I give people a try as in if I am interested in someone, should I hang out with them and see how it goes? If so, what qualities make a good and trustworthy friend?