I am terrible at it...
Today I was in the store with my mom and we bought 5 gallons of refilled water and I forgot to pay for it, so I went back to the cashier and she rang it up as $1.45 and I didn't have it, so I was scrambling through my bag trying to find $1.45 and a lady behind me asked the cashier, "How much are they short?" And the cashier said, "$1.45." And the lady gave the cashier $20 and said, "Take out how much they owe out of that."
I was SHOCKED! I didn't want to take it, but she said, "Please pay it forward, do something kind for someone else." I was so happy, I am definitely going to pay the kindness forward.