L.R.
Check online for the regulations in your area for licensed day care providers and be sure your chosen provider is licensed by the county or state or whoever does licensing in your area. Check to see if a caregiver has any outstanding complaints against him or her -- I believe you can get information about that from the licensing authority.
Listen to the mom who said, go with your gut. You should visit each daycare and they should be happy to let you go anywhere in the facility -- if they seem reluctant to let you see everything, that's a red flag. If they discourage parents from dropping by unannounced, that's a big red flag; any daycare should be fine with parents coming by unannounced at any time.
Also, be sure that the caregivers are not just parking kids in front of a TV for chunks of the day, or at all. A friend didn't realize for quite a while that her kid was spending much of each afternoon just watching cartoons at the day care provider's house -- not, in my opinion, a good use of anyone's time, and indicative of lazy caregiving.