How to show Friendliness to those Worthy of it?
The Blessed Buddha once said:
Bhikkhus, those who you think is worth listening to & for whom you
feel pity - whether friends, family, colleagues, or just associates -
all these you should explain, establish and settle in developing these
Four Foundations of Awareness. What four? When a Bhikkhu keenly
contemplates:
1: The Body just as a formation...
2: The Feeling just as a sensation...
3: The Mind just as a passing mood...
4: The Phenomenon just as a mental state..
while always acutely aware & clearly comprehending, he thereby removes
any greed, envy, jealousy, frustration & discontent rooted in this world...
Bhikkhus, those who you think is worth listening to & for whom you
feel pity - whether friends, family, colleagues, or just associates -
all these you should explain, establish and settle in developing these
Four Foundations of Awareness...

Details On Foundations of Awareness (Sati):
http://What-Buddha-Said.net/drops/What_is_Right_Awareness.htm
http://What-Buddha-Said.net/drops/III/Awareness_Sati.htm
http://What-Buddha-Said.net/drops/Clear_Comprehension.htm
Source of reference (edited extract):
The Grouped Sayings of the Buddha. Samyutta Nikāya.
Book [V: 189] 47 The Foundations of Awareness: 48 Friends..