You should be open-minded, passionate, honest and kind. Whenever your friend is in trouble, you will always be all ears and share his sorrow. By no means will you abandon your friend when he is sad or unpopular. In this way, you will be able to make friends with many people and maintain the sincere and valuable friendship forever.
Futhermore, you should learn how to forgive your friends when they offend you accidentally. Being generous to others equals to being generous to yourselve