i've learned to really enjoy looking at fakes. they often got a charm and ingenuity all their own and if they prove themselves to be legit then it is a very pleasant surprise indeed. for $5 the lesson will be etched onto your consciousness.
imo it also helps to go to nords or wherever and get a look at the genuine article and any known legit vintage specimens you can get your mitts on.
hot tip: most of the heavily branded "lux" stuff you see in thrifts will be fake.