A most excellent list http://www.magnet.state.ma.us/dph/qtool/spttop.htm

And some other things...

How are internal communications handled?

How are difficult patients handled?

How far into the disease can people stay?

What's employee starting salary?

What's the pass/fail ratio of trainees?

What's the daily activities schedule like?

How are complaints handled?

Tour the kitchen.  If it's clean and busy that says a great deal of good about a place.

Get references.  Talk to the families and residents who are not memory impaired.  What do they have to say?

Make a surprise visit or two or three.

Do more research than you think you need to.