Advertise your business in a way that comes clear that you're offering a cleaning service. You would also have to compile a list of what's going to be cleaned on a regular cleaning session.

You can also offer discounts to clients that require your service twice a week for example or if you know they referred you to another person.

Purchase a liability insurance for your business. You need to be protected against lawsuit in case a client suits you for causing any harm.

Please pay extra attention to this: many clients work long hours, and they are not home during the day, and that's when you do the cleaning, so make sure you buy a safe to keep the keys that clients give you, away from anybody who is not part of the business.

Take a look at this website and see a How To article on operating a business successfully.

Hope that helps