Be polite and courteous. As St. Basil observed, “He who sows courtesy, reaps friendship, and he who plants kindness, gathers love.”
Smile. A sincere smile disarms the guarded, soothes the argumentative, calms the angry, and encourages the downhearted. It sets a positive tone.
Be optimistic. Everyone has enough problems already. People are drawn to upbeat, solution-oriented people.