Hi,

Miatas are very well built, so general wear and tear is still pretty small
on well looked after miatas even on the over 10 year old examples.
Its generally considered that after 94 the cars had many improvements, both
in chassis and engine.
94 and 95 are generally considered the best years for a NA, after 95 the oil
pressure meter and a few other engine management electronics were changed,
so if possible try and get a 94 or 95, to be honest after 94 there is not
much in it, but personally I would look just a little bit harder/longer and
get a 94.

The rear window and get badly damaged over time, if the previous owner has
not unzipped it properly then it will eventually lead to it splitting, but
that is something that is very easy to spot.
Other than that check what you would usually check, things like body panels
(has it been crashed badly) id tags (has it been stolen) service history,
check the oil make sure it is in good condition and not contaminated, the
tire wear make sure the car is aligned properly, check the pedals to see if
the pedal wear matched the mileage.

I think AC is a must have option in Aus, other than that its what ever pulls
your chain, ABS, central locking, heated seats, cruise control, electric
windows, electric mirrors, airbags, they can all be found either factory
fitted or to add later,
The jap Import Eunos is a good buy, generally has AC, nice light alloys,
electric windows and mirrors, and a bonus for me no ABS or airbags.

Cheers Mark.

From miata.net:  http://www.miata.net/faq/usedmx5.html

Get in touch with your local club:  http://www.mx5.com.au/

Come along on a drive/track day/BBQ/etc. and you'll get all the hints
and tips you need.  :)

all that good stuff plus this little tip...  if you buy in the off season
(winter) you pay much less.