There are three types of 'friends'...

Those that are necessary like nourishment and you cannot live without them; those that are like medicine and are beneficial, so you need them sometimes; and finally, those that are like a sickness and you do not need them at all!
Prophet Muhammad (saw) has said, "The believer is like a mirror to other believers (in truthfulness)." Like a mirror, your friend gives you an honest image. He forgives your mistakes, but does not hide or exaggerate your strengths and weaknesses.
Once Prophet Muhammad (saw) was asked, "What person can be the best friend?" "He who helps you remember Allah (SWT), and reminds you when you forget Him," the Prophet Muhammad (saw), counseled.
Imam Ali ibn Abi Talib (as) said: "A friend cannot be considered a friend unless he is tested on three occasions: in time of need, behind your back and after your death."
Imam Jafar Sadiq (as) also remarks, "My best friend is the one who gifts me my weaknesses and shortcomings." In other words one who brings to your notice your defects and flaws is indeed your true friend.
However, there is one very imperative point in the above-mentioned tradition of Imam Jafar Sadiq (as). When one presents an offering to a close friend, he does so with utmost care, not willing to overlook anything. He offers the gift with total respect and regard. For, even the most valuable gift if not presented with correct etiquette, can look very ordinary. While presenting the offering, the friend tries to make the most expensive gift seem very ordinary so as to not embarrass the recipient. On the other hand, the recipient of this gift tries to make even the most ordinary gift seem very precious, so as to please his friend. Similarly, when we wish to point out certain shortcomings to a friend, we must do so with a degree of respect and sincerity. Our sole intention must be to reform the friend and there should be no hint of any malice and self-righteousness. Likewise, when a friend highlights for us, our defects, we must acknowledge the same with respect and gratitude without any ill will and hostility.
Imam Hassan Askari (as) Says: "Those who advise their friend secretly are respecting them, and those who advise them openly are humiliating them."
Indeed if we establish these as the standards of friendship, the believers shall soon find themselves enveloped with friends who will take them closer to Paradise and farther away from the fire of hell.
Allah (SWT) says in the Noble Qur'an: O you who believe! Take care of your souls; he who errs cannot hurt you when you are on the right way; to Allah is your return, of all (of you), so He will inform you of what you did. (Surah Al-Maeda, 5:105)
There are certain tips to remember if you wish to keep a stable friendship.
Do not dispute with him and do not be hostile to him.
Do not ridicule him. Do not quarrel with him. Instead accord friends the respect they deserve.
Imam Hassan (as) Says: "Befriend people in the same manner you would like them to befriend you."
Do not hold him in contempt nor consider him to be lower than you. Instead guard the honor of your friends during their absence and after their death.
Do not claim precedence and supremacy over him. Instead forgive the short-comings of your friends, because everyone makes mistakes in life.
Do not crack indecent jokes with him.
Finally, we ask Allah (SWT) to make us of the righteous ones and give us companions that will take us away from His Wrath and lead us to His Pleasure and Paradise.