Don't know if this will help you mate, but this is what one of my competitors does where I am. He comes from over 60 miles away to the areas I work in. (Soldiers houses). He sticks a note on each door on each street that says "WE are in this area tomorrow to clean windows, if you would like them cleaned please tick the box, Price is XX " This guy is part time by the way.
This means he comes down to the areas one day, goes home, comes back the next day and sees who has ticked the box and remembered to stick the note back on the door or window. From what I've seen, he gets about one in thirty that haven't already got a window cleaner. So a crap result. If he'd knock doors and ask, he'd get a lot more, but door knocking makes some grown men cry with fear, so he never gets any regular customers.
He's cheaper than I am, and cleans to an OK standard, but has this mortal fear of knocking and speaking to people. Got another bloke that is mostly full time gardening and does some windows on the side. He takes on any Brit custy he can get and tries to link jobs together that are miles apart and miles from where he lives. So never gets any sort of order to his window work. Keeps losing his window custies because he's unreliable. Another great guy to have as competition.
These guys are great to have around. Makes life so much easier. Notes in windows etc has all been done, and may work to a certain degree, but I suppose the moral is, try not to cut corners, just knock and ask. It's what separates those with a big list of custies from those who don't.