Years ago I attended a ridiculous training session at work. The only thing I recalled was making a compliment to someone can really make someones day- either a shop worker, someone you've just met at an event or someone you already know.
I don't make it my mission to complement every single person I see, but its lovely to see someones face light up when you compliment their earrings, blouse, shoes etc. Especially if they are doing a mundane type of job where they are dealing with often shitty general public all day.