If you want to get a leg-up, there are many sites on the Internet to help you along. AFV recognition is actually fairly difficult (for many people), so I would suggest getting a head start (work on the basics: Canadian military equipment (go to DND site for photos) and then NATO equipment. It‘s kind of like being able to tell the difference between a Honda Civic and an Accord: they basically look the same (4 wheels, roof, trunk, etc), but it‘s the details that you have to pick up on. So it goes for AFV‘s and AC: to the untrained eye, an M1 Abrams Main Battle Tank looks like a Challenger MBT, but one is US and the other from the UK.
Basically it‘s nice to have a photographic memory (they used to use slides to test you, and there were only so many photos of some of the old Warsaw Pact vehicles, so it made it easier). Now they can use computer generated models to make it much more difficult, so you actually have to know what the vehicles look like from every perspective (**** technology!!!!!).
Anyways, hope that helped.
Allan