I would start with my state's Office of Care Child. Each state should have an office that is responsible for giving out licenses for daycare facilities. They should be able to not only give you a list of such facilities, but to give you lots of valuable information about if there have been any sorts of complaints, problems or issues at the facility. When I was researching, I actually got to speak to the person that visited the daycare facility and she gave me first hand information of her opinion of the place.
Another good resource is the NAEYC (National Association for the Education of Young Children) - it is a national organization that many daycare facilities try to become members of - as they have very stringent guidelines of daycare facilities. You could still have a very good high quality daycare facility that is not a member of NAEYC, but if it is, you have some assurance that it will meet certain criteria.
Also go to
www.carefinder.com. I got lots of good information including what to look for at a child care facility, who to contact in your state for the Office of Child Care, questions you should ask at a facility, what a facility should have, etc. It is a wealth of information. This website should answer all your questions.
A key thing that I found most parents not doing (and I really don't know why) is to ask for references. I received several parents' names and called all of them and asked how they liked the school and talk with them at great length.
Sozobe is right (not that you wouldn't), but make sure you visit at each facility you are considering. Right away, I knocked several off my list just because of the visit. One because simply the director had a piece of spittle hanging from his mouth and seemed a bit disheveled. I thought, if he is messy, how clean is his place? That is where the trust falls in. After all the work I did (and my daughter was 4 when I first placed her - only two days a week), I left the facility feeling good and comfortable that they would properly care for her.