1. Appreciate Good Qualities.
When we appreciate other people's good qualities we strengthen them. When we appreciate their good qualities, we avoid feelings of jealousy, we help to make these qualities part of ourselves. Admiring the good attributes of others, is also one of the best ways to inspire our friends. Our friends will definitely appreciate it, when we recognise the good things that they do.
"Love your friends. Honour their good qualities. You will have joy and peace in boundless measure."
- Sri Chinmoy 
2. Attitude of Forgiveness.
When our friends do thing that are wrong, or cause unhappiness, the best thing to do is to maintain a forgiving attitude. Here, forgiveness is not in a condescending manner; forgiveness of friends comes from a sense of oneness. If we can feel that this mistake is something that, we ourselves, could have done, then it will be real forgiveness. In addition to forgiving the mistakes of our friends, we should also try to forget these unfortunate experiences. If we forgive, only to hold it against them at a later date, this is not real forgiveness. When we truly forgive our friends, they will be inspired to try and overcome their weaknesses.
3. Good Communication
A Good friend is one who we can share the important events of life with. If we are able to share problems with our friends it will be a burden off our shoulders. At one time we may be helping our friends, at other times, our friends will be helping us. To real friends, there will be no difference between the two.
4. Sharing Humour.
If a friendship is always based on seriousness and gravity the friendship will be dependent on the judgments of the mind. If we can find time to enjoy life and share humour it will help to maintain a good friendship. Humour is one of the best antidote's to the teeming problems of life.
5. Never Speak ill of Others.
The nature of the human mind is to enjoy gossip, but when we speak of others bad qualities we will lose the trust of our friends. When we speak ill of others, we should feel we are actually criticising part of our extended self. If we have this attitude we will not wish to cause pain to our friends and ourselves. No good ever comes of gossip; if others start criticising our friends we will change the topic of conversation or not allow.
 The language of the Heart by Sri Chinmoy: AUM publications