Smiling

Smiling can be a good gesture when to replace talking, greetings or other expression. Just count how many times you greeted good mornings to your friends or strangers, you would be surprised you only smiled to 100 percent of straingers and 60 percent of your friends when you are on your way to work.

Sometimes you smiled when somebody asked a question which you cannot answer. Smiling when taking a photograph most of the time. 

You smile to everybody you met. Sometimes you smiles during awkward situation to lessen the tense of the moment. For example you dropped something, and afraid getting scolded, you just smiled.