What are some things that make you really happy?

To make someone happy with our little efforts.
Most of you guys must be working in a firm. Everyday you enter your office and see the security Guard who stands at the Gate, house keeping staffs who cleans your workspace often greet you. And how many times have we responded them with smile ?
Quite a few time I guess. So, develop a habit of greeting them before they greet you and you would be elated when you see the satisfaction and smile on their face.
It only requires a little effort to be happy and to make someone happy.