What are the qualities that a best friend should have?

A best friend should have good values. A best friend should have the effect of making you a better person through your association with them.

One Bible proverb puts it this way: “He that is walking with wise persons will become wise, but he that is having dealings with the stupid ones will fare badly.” (Proverbs 13:20) Many people select friends merely on the basis of whether they “hit it off” or not, how they feel when they are around them. Naturally, we like to be with people who make us feel good. But if that is the only criterion for our choice, with little or no thought given to a person’s real inward qualities, we may be headed for great disappointment. How can you know whether a person has good values?

To begin with, we must have our own good values. We need to know what is right and wrong, good and bad, and hold firmly to high moral principles all the time. Another Bible proverb states: “By iron, iron itself is sharpened. So one man sharpens the face of another.” (Proverbs 27:17) When two people bring ironlike moral strength to a friendship, they can help each other to grow, and the bonds of friendship between them will be stronger.
Our best friends, whether they are young or old, are those who help us to stay headed in the right direction and who correct us when we are about to do unwise things. The Bible says: “Faithful are the wounds of a friend.” (Proverbs 27:6, King James Version) To strengthen ourselves morally and spiritually, we need to associate with others who have love for God and his principles
If you are interested in making friends with someone you have met, you might want to ask yourself, ‘Who are his or her friends?’ The type of close associates someone has tells much about the person himself. Also, what opinion do mature and respectable people in the community have of him? In addition, it is wise to consider not only how potential friends treat us but also how they treat others, particularly those from whom they have nothing to gain. Unless a person displays good qualities, such as honesty, integrity, patience, and consideration, at all times and to all people, what guarantee is there that he will always treat you well?
Getting to know someone’s true character requires patience and skill, as well as time to observe the person in real life.

The Bible states: “Counsel in the heart of a man is as deep waters, but the man of discernment is one that will draw it up.” (Proverbs 20:5) We need to talk to potential friends about serious subjects, those that reveal their true personality, motivations and, yes, values. What sort of people are they? Are they kind or cold? Basically positive and cheerful or negative and cynical? Unselfish or self-serving? Trustworthy or disloyal?
If a person talks critically about others to you, what will prevent him from talking negatively about you behind your back? “Out of the abundance of the heart the mouth speaks,” said Jesus. (Matthew 12:34) When it does, we should listen.