1st Gen Barracuda ?

I'm pretty much a 2nd gen Fishy fan and spotting the years is really easy! I don't know how to tell the difference between a '64, '65 or a '66 Barracuda. What do I look for? Is there a difference in tail lights, grilles, trim packages? There's a few here in the area and I'd like to know how to tell what is what. Thanks in advance. (yes I do know the fast back was the fish, the coupe was the Valiant :P)