How do you write a campaign pitch?

I have a project for school. I have to write a campaign pitch for conserving water. It has to be 3 paragraphs long and it has to have an argument like,"Isn't water just recycled? We don't need to conserve it." something like that. Im not saying you have to do it for me just give me a format because the teacher didn't tell us anything. everything helps!! thanks in advance.