J.B.S.
A cleaning service should be chosen by first defining needs and wants and developing a plan to meet those needs and wants at the most economical price.
If cost is your most important factor, make this known when calling potential service providers. There are many inexpensive service providers available, however, with lower costs you may be sacrificing quality, consistency and reliability. If quality, consistency and reliability are important to you, then you should look for a company with high standards in their cleaning services while having a management team, processes, and infrastructure to provide you with your desired standard of service.