Can't beat door knocking.
Get a street with dirty windows, or where you only have a few customers, or where someone has said "we never see a WC around here" - bite the bullet and go out in the evening.
Between 5:30 and 7:30 ish works great.
Knock door - big friendly smile
"Hi, my name is X, I'm a window cleaner. I am cleaning a few houses in your street so I though I would knock all the neighbours doors to see if they would also like a regualr window cleaner."
Yes = Would you like a quote now
No = Could I leave you my card in case things change in the future.
Boom boom, bobs your mothers brother.
Cheers
Steve