Facebook is good but not if you go about it in the wrong way. I opened a facebook account for my firm but that on it's own wont pull much work. The way I do it is, find people you know who are in groups. Then join those groups and place an add. Make sure that when you join the groups, contact the admin and/or creator and ask them if it would be OK for you to introduce your service. They usually say yes.
Opened my group about mid December and so far have over 150 members and about 3K worth of work off it since then. I don't advertise window cleaning on it though, I just use it for the carpet & upholstery cleaning part of our biz. Should work just as well though for WC work.
If you need help mate, give me a shout, my e-mail is on my profile, and I'll show you how, where and what I post to get a result.