3 предложения по теме, как стать хорошим другом. Простенькие, но хорошие.

First of all, I believe you have to listen to your (future) friend very carefully. It's quite for people to realize they are listened to.

Secondly, I reckon you have to care about your (future) friend. People do appreciate somebody's help. "A friend in need is a friend indeed"

And the third reason is your reliable. You have to keep your promise everytime. Only in this case, people will trust you and never let you down.