If you hire a cleaning service, Don Aslett and Pam McClellan, authors of books on cleaning, offer this advice:
Get a firm bid.
Make sure cleaners have liability insurance.
Never pay in advance.
Be specific about what you want and expect.
If you have delicate items, or objects of great value, put them away or excuse the cleaner from cleaning them.
Clarify other issues: Is it all right if the cleaners use your phone and drink your soda? If you're not home, what are your options for giving the cleaner access to your house?