ive done door knocking for years.. so i suppose im biased
i really dont think theres any secret though other than smiling and being nice - genuinely , people smell if your fake so if your not a nice person pay someone else lol
but seriously , just do it , theres only one way to get used to it and thats doing it. Oh and in all the years ive knocked doors - full time for a few years at one point , i can honestly count the bad experiences on one hand, and they were only old men and nutters , you can come across them when cleaning anyway
99.9% of people just want to know why your at the door quickly, if you smile you give yourself a few seconds to tell them, also when you say your building your window cleaning round most people understand and will be fine
most around me are scared of giving a window cleaner the job if its not his patch ! Even the customers are trained into that rubbish . You want to drop leaflets here , nothing but threatening calls , i just laugh them off , you need a bit of a thick skin to survive if you want to build your business and deal with strangers and upset window cleaners
Good Luck , but just do it ! the work wont come to you , maybe read some motivational stuff from salesmen and entrepeneurs to boost your willingness to get stuck in.