I think it is so important to try everyday no matter what you are doing or where you are to be kind to people. A little act of kindness goes a long way. So I always try to wish people a 'nice day' whenever I leave. If I am in a shop or randomly chatting with a stranger I always aim to say 'have a nice day' whenever I leave. If not then even a smile can go a long way too. Somebody can be going through the toughest times and your little friendly gesture can completely turn there day around. Just a smile or a few words can go a long way.