Walk down the street and notice if someone in front of you drops shoe shiner's tools. A brush or polish are two types of tools that can be used.
Pick up the tools, run to catch up with him and return them to him.
Listen as the potential scammer expresses his thanks and start a conversation with you. A scammer will likely have a story to go along with the brush--he may claim that it's the only brush he owns, that it was a treasured relative's brush or he may use another line to illustrate the importance of the brush in his life.
Receive a gesture of thanks. The scammer will offer to shine your shoes for free to thank you for your kindness.
Move to a place where the scammer works. He may have an area set up for his shines or he may take you to a place where he easily can shine your shoes with a portable step.
Listen to the scammer's full story. The purposeful dropping of the items combined with the previous anecdote were meant to get you to a place where you're forced to listen to the story. While having your shoes shined, you will likely hear about the scammer's supposed financial troubles. The scammer will keep shining your shoes until you've heard his entire story or until you seem to express compassion.
Pay the shoe shiner. The scammer will expect a more than generous payment and tip in response to his story. Some scammers may even ask for a specific amount of money to help pay off one of the bills they mentioned in their story.