Every one has there own way of doing things, but I'll tell you how I done it when I started.
I would choose an area that I wanted to work in, I would then go out late afternoon(more people at home) and start knocking. I would say (and still do) "Hi I'm trying to expand my window cleaning business in this area and I was wondering if you'd be interested in my service".
If they said yes or maybe, I would give them a quote and the frequency between cleans 4 or 8 weeks for me) once I had there details I would give them a flyer so they had my number and then I'd say when I'd be back to clean them. Also don't forget to tell them about how they pay you, if you have an evening you go out collecting or if you leave an addressed envelope ect.
I have experimented recently with leafleting an area then going back door knocking a few days later, but the results were no better in my opinion and you've walked the streets twice.
Also I wouldn't make an issue out of how you clean the windows unless the customer asks, they don't realy care as long as there windows are clean. I've recently started using wfp and I've found most customers don't care, I've just had a few asking is this down to health and safety, then I just expain the benefits to them and to me.
Good luck