We start with lessons in every classroom. At our first day, we place the containers in the school, so all the students know where to collect the lids after we told them about the project. They collect these at home, ask their families, ask restaurants and supermarkets. We encourage them to be creative, but emphasize that they shouldn't buy many new bottles just to collect the lids. It's about the plastic that is already part of a householding and that otherwise would turn into (useless) waste.