Look for a 5spd hehe! Don't know if it is your first car, but these are the basics I heard.
I don't know where you're from, but rust is a main factor around here. The hoods on Mazdas rust pretty fast so check it out, I had some on the two rear fenders as well (got it all fixed by Mazda on waranty). In the test drive, check anything you could hear/feel which doesn't seem right. 25K seems damn low for a 6 years old car, make sure it isn't too good to be true! (If the shift knob or pedals seem really used... it might be)
I'm not much into mechanic, so you might want some more technical advices, but I'd say, make sure you fall in love with it! And welcome to the best Mazda forum around if you join us! (drinks)