I am a little unsure about secret, but if you are referring to random acts
1. Open or hold the door for a stranger.
2. Compliment a stranger.
3. Tell someone you haven't already told how much you care about them.
4.Find someone who looks miserable, and tell them to smile.
5.Smile at a stranger and say "hello".
6.Stop and let the car trying to pull into traffic, allowing them to go before you.
7.Send a card to your local fire department thanking them for what they do.