A true friend would tell you the truth. If you looked or was being ridiculous they would tell you instead of you making a fool of yourself. A true friend would stay your friend though good times and bad times.
Not considering temperaments,i can say that a TRUE friend is one who is ready to do just anything to make one happy.He understands his friend and knows how to deal with him.He's always ready to sacrifice as the bible explains in 1John 1.