Not sure if you’re a people person or not, but be ready to step outside of your comfort zone. Most people find talking to strangers uncomfortable and usually tend to avoid it. You need to be able to find common ground and develop a rapport within a minute or two. This will get your foot in the door so they feel comfortable with you. If you can’t do that the conversation will be forgotten the next day. This is huge if they have someone, and decide to keep them for the time being. If anything with their current goes south, they’ll remember you and call.
Like @GSARMedic said find out if the have a cleaner, how happy, how can you offer a better value. Not necessarily a better price. And be prepared to let the sale drop if it isn’t a good value for both of you. If you’re giving an extremely low price, they may be happy but you won’t be and your consistency will drop eventually and in turn they won’t be as happy. If it’s too high a price, you’ll be great and happy, but they will be more likely to accept bucket bobs service when he comes calling and then you’ve lost an account.
Marketing in the service industry for smaller businesses is all about people skills. You could be the best window cleaner in the world, but if you can’t sell or have someone who can selling for you, you’re out of work.