The most important quality a friend can have is trustworthiness. Trustworthiness is one of the most important qualities in life. It is the quality on which all relationships are built. Being able to trust the person means that you both can do much more together. All of my friends definitely have this quality. I like to consider myself a trustworthy person, but since i can't judge myself from a different perspective, i don't know what others think of me. To improve yourself on this quality you should be a honest person, stop gossiping, be transparent, and keep your commitment in word and deed.