If you are just starting out, and don't have many customers yet, then the very best method is to leaflet an area on ie a monday, put on the leaflet that you will call around at an approx time the next day, then knock on their door when you said you would, I did this on a new estate, and picked up 100+ customers in a week, out of 300 houses on the estate. Once I built up a reasonable customer base, I didn't get time for door knocking, but have had good success with leaflets, I only target properties that I want to do, ie big houses in wealthy area's.