So what are some of the things you should look for or ask about when
visiting a school?  Number one, ask about the class schedule.  If classes
only meet when you can't attend, it crosses the school off for you.

Another thing to look for is who is teaching the classes.  Often, the
person teaching your class won't be the head instructor.  Frequently the
head instructor will have some of his advanced students teaching classes. 
This is particularly true if the school you choose has separate classes for
lower ranked and higher ranked students or if they have a "new student"
class. Don't let this dissuade you.  Often instructors teaching "new
students" are doing so because they have shown an aptitude for helping new
students learn the basics of an art, perhaps even beyond that of the head
instructor.  The ability to _teach_ a physical skill is often dissociated
to some degree from the ability to actually perform that skill at high
levels.  Most professional boxers could whip the tar out of their coaches
even though their coaches know how to box.  While on the topic, find out if
there is an "introductory" or "getting started" class or course.  This can
be a good way to get up to speed quickly with the basics of an art or to
"sample" that school.

While visiting a school, spend some time talking to the students before or
after class.  Talk to both high and low ranking students, they'll have
different perspectives.  Spend some time understanding the atmosphere of
the school, it will take more then one brief visit.  Some are strict
disciplinarian and some are easy camaraderie.  Again, don't assume that the
instructor that runs his school like a drill sergeant produces kick-butt
martial artists while a more easy going school is lax or lackadaisical.  They
are simply different teaching styles and one may be more appropriate to
your needs then the other.

Another thing to take note of is injuries.  Let's face it, martial arts are
inherently dangerous.  They are _martial_ and no matter how safe you train
or what safety equipment is used, there is a risk.  There are bound to be
some injuries.  However, the nature and frequency of the injuries are what
you should consider.  A black eye is far different from an injured joint
and if broken bones occur frequently, that may indicate a problem.  You
can't train while recovering from some injuries.  Some injuries are
permanent and will affect you the rest of your life.

Finally, though uncommon, some schools have an "enrollment period."  They
operate like college classes in that you can only join at certain times of
the month or year.