The best way I've ever found is to ask my neat freak friends. Often times the best cleaning ladies are the ones who speak practically no English and are just doing cleaning on the side for some extra money. (Sorry to say, the Merry Maids of the world are terrible in my experience - all the licensing and bonding in the world can't make up for their inattention to detail!) So interviewing them (for me) is silly, because my Spanish is terrible. :) My usual process is to walk through the house with them so they can see how we live and how much stuff there is to clean. They'll give a price for the first-time cleaning (which will always be more, unless you are a super neat freak yourself). They may want to know if you expect your laundry to be folded, bed linens changed, refrigerator cleaned, etc, or if you just want the "basics" such as floors, windows, bathrooms, dusting. (Although a really fantastic cleaning lady will do it all, because the best ones can't STAND to leave stuff undone!)
Then, once you've agreed upon a price, have them clean your house. I would make sure to be there the first few times in case they have any questions (such as where the garbage and recycling bins are, where your extra Windex is, etc), and to make sure you're comfortable with the job they're doing and can offer corrections if needed.
Our current cleaning ladies have a key to our house. Not a single dime has ever gone missing, and they get the house SO clean that you can literally smell the clean from outside the front door. I knew they would be good during the first cleaning when one of them came to ask me for a tall ladder so she could clean the chandelier in our foyer and replace a light bulb that had burned out. It was like the heavens had opened up and angels were singing. :)