Compassion without the passion

Greet someone different every day, that you otherwise wouldn't have.

Try greeting strangers. If you feel funny about it, greet strangers who you're least likely to bump into again, for example, if you're in a city or place you aren't often in, or if you're in a place where travelling people stream through.
Greet people you know but haven't greeted for a while. The lack of a clear motivation for a greeting takes things outside of the box. It's nice to think that someone thought of you without having to be prompted by the flow of events.