Doesn't matter a great deal what you say. What does matter is to be polite, courteous & friendly. Canvassing is largely just a numbers game. Once you find the individual who potentially may be intereseted in your service, the challange is to establish trust as soon as they answer the door. If they do not want a window cleaner, there is no point having a long speal each time. You are just wasting their time & yours.