Stand in an area with a lot of foot traffic and a narrow sidewalk. Be friendly but assertive, and hold a leaflet in front of everyone walking by. Say something short and inviting like "Info on helping animals?"
Your body language is key to improving your "take rate" when leafleting. You'll get the hang of it with time, but these tips will help speed you along:
Confidently walk toward people to hand each of them a leaflet; don’t just stand still and wait for them to come to you.
Extend your arm fully while they're walking toward you, so the leaflet is in front of their stomachs.
A genuine smile, eye contact, and a loud but friendly voice are key.