I mean the attitudes, not the decor. Look for healthy and unhealthy attitudes. You MUST visit a school more than once in order to form a valid opinion. That is, unless you get the high-pressure sales pitch and walk out the first time. But aside from that, if you only visit one class, you'll still have no idea what a typical class is like.
Classes vary from one to another.
There are good days and bad days for everyone, even instructors. The usual instructor may be on vacation. So when narrowing down your choices, visit more often so you can get a good idea of what it would be like to train there. Be aware that many schools do not have continuous enrollment. This is pretty much par, so don't let this offend or discourage you.