How did Japanese tactics in the defense of Okinawa differ from those on other islands in the Pacific?

Brettd is, as usual, right on with his answer.  However, I
would add one thing to his answer that will supplement it, not dispute
it.

As he says, the main difference was that Ushijima
defended in depth.  But the point that needs to be made here is that he was trying hard
to defend for as long as possible and to inflict the maximum possible casualties on the
enemy.  This may sound obvious, but this is not really how things were always done.  In
many cases, other Japanese commanders opted for what the Japanese called "honorable
death" instead of fighting for as long as possible.

The
Japanese word for this "gyokusai" and it is written like
this:

玉砕.  That first character means "jewel" and the
second means to break or crush.  That shows the Japanese attitude towards death at that
time.  They felt that their own deaths and how they happened were more important than
killing the enemy.

Because of this, Japanese commanders on
places like Saipan tended to order "gyokusai," or what Americans called "banzai
charges."  These allowed the soldiers to die in an honorable way, but they were much
less effective than holing up in caves and fighting to the death would have
been.

On Okinawa, Ushijima forbade such things and for the
most part made that stick.  Thus, his defense was much more deadly than that mounted by
other commanders on other islands.

So, I'm agreeing in
general with BrettD.  But I would shift the focus to the idea that Ushijima's goal was
to kill more of the enemy and delay their victory, not to ensure that his own soldiers
got an "honorable death."