Medicare has a star rating system - but that system is not always accurate the grading scale seems to vary widley
The particular nursing home your considering may have failed state inspections and had numerous lawsuits and still can have a 5 star top quality rating from medicare.

How To Really Research a Nursing Home

Look for your self
look up the county courthouse public records for law suits against a particular nursing home - many suits are settled out of court and do not end up in the publics eye - one good way is to look at the public records at the county courthouse or - online (I'll have some links up soon)
Another is to look up state inspection reports of the home - not medicare inspections - but acutal state inspection results -