You can go to the Medicare site for their ratings:
Medicare.gov - Nursing Home Compare
When I am job hunting I usually look at this site. Unfortunately, sometimes when I go to the nursing home that looks like it has good ratings, I find it is a pit of despair. You do have to go in person and check it out. Also, some states on their Department of Health sites have all the State survey results from their inspections. You can also do a search for JHACO or State survey results.
You want to look at the type of complaints, are there real quality of care concerns, numerous medication errors, wound issues, infectious issues, abuse or neglect issues, and how do those compare with other facilities. All facilities have their glitches, but a facility with a large number of quality of care deficits obviously has some serious issues.
Also, the type of tags -- are they A, B, C.....which range from isolated incidents, to potential for harm, to actual harm. The higher the letter, the worse the level of care.
Of course the best thing is to walk in the door. Does it smell like urine? Not good. What do the patients look like? Are they clean, is there lots of activity going on, or are they all confined to their rooms? Is the floor buckling with decay? How do the employees look? Do they look happy? Sour? Stressed?
The other thing is how HR treats you. Do they offer you a job the minute you walk in the door? Probably they can't hold onto staff and are desperate.
You really have to be careful. Especially with the for-profit facilities, because they are all about the profit margins, and will skimp on care to get the biggest profits.