This might be an obvious statement, but i'll say it anyway. The more people see you cleaning windows the more customers you'll get, it is the best advertising you can get. When people see you acting professional and doing a good job, they will come to you.
I use leaflets and canvassing to some success but it is hard work. Don't expect many replies from the leaflets, but at least people will know who you are when they see you walking about on saturdays.
Working Saturdays will work well coz more people will be at home and see you, so be wary they will be watching you constantly wondering who you are.
I've started walking everywhere, even if it would be easier to drive. This means more people will see you. I've now started picking up new customers on the roads between old customers.