I think Eric said it right the first time.
Other factors that play into martial arts schools are: what do you want to accomplish?
If you want to learn how to fight start checking the full contact places out.
If you want to look pretty check out the Tradititional arts.
Some factors I look for to determine if a school is more Fluff than Tuff.
Number of Kid's to Adults. If kids out number adults it means no contact. (Alot of schools are just another way of babysitting kids)
Number of belts, if each belt has four levels before promotion to the next one, and others follow the same pattern. That's a warning sign.
If there are like 20 black belts in that art for one class that usually means pay us 3 years of dues and you'll get your black belt.
Ridiculously, long Bow in/out Ceromonys (i.e. 30 minutes) usually sign of a cult.
If the head instructor is called "Master", "The Master" it's generally a bad sign.
If you hear Supernatural Stories of "The Masters feats of super human greatness" That denotes cult like status.
Any Martial Art School that tries to blend any biblical or religious term into title of martial arts they practice. I've seen this done with my style of Ju Jitsu. It's very heart breaking for me to see the abuse of my style's founder, for some one elses profit.
If the head instructor is 28 and has a 10th degree blackbelt. Anything, more than 3 rd degree is suspect.
If you get a gut feeling about the place go with it.
If you have to buy a different color uniform for each promotion level. This a definate rip off. We have a school in my area that does this, very cult like. i.e. class assembled looks like a box of Skittles.
Any school that promises "enlightment" if you train with them.
There are changes in you that comes from training, but it's not because the school gives you the philosphy. It's because the changes come from within you,and happen slowly overtime as a by product of training. Not by a Wanna be Guru of eastern philospy.
If the term "unique style" is used this usually translates too:
"I've taken only the moves that work for me very well in my orginal style, and chose not to teach the ones I did poorly or fail to understand with out failing to comprehend the different body mechanics of other people in mind who might be able to use the moves I do poorly in well"
"I trained a month here, a month there,don't hold a belt in anything, and dropped out due to ego, I only teach what ever one move I picked up on at any of the twenty places I trained at in three years"
"I made it up"
This has happened in my area with a guy calling his style "Tai Fi" he's in jail for fraud, and some other charges as well.
Also, alot of the Flim Flam artists will move to areas with no competition, because it easier to make money with no one else around.
Remember, Martial Arts is an unregulated field there is no real governing bodies. Therefore be aware and use caution when selecting a school.