Friends are honest companions in life who have your best interests in mind. They are people whose company you enjoy and whom you share common interests and pursuits with.
Good friends are able to put aside their self interest now and then to support you and demonstrate care and concern for your life events good and bad.
It's important to realize who your friends are in life and to make good time for those people with the kind of support you enjoy as well. The Golden Rule is a good process to follow, "Do Unto Others As You Would Have Them Do Unto You."