Where exactly is the oil filter on a 1997 Mazda 323F?

Depends on the engine, but on the 4 cylinder models if you open the bonnet, and stand with the car facing you, the oil filter is right in the middle, on the back of the engine (Facing away from you). Its screwed in, and you may find it easier to drain it by puncturing it with a screwdriver before you try and unscrew it, because else it'll spill everywhere (It holds a surprising amount!)