Basically if you have a question takes pics and post and the community will do our best to help you identify them. The differences are subtle but they are there. Once you start to see the differences they become more apparent when you see them again. Takes time and practice much like everything else.
Go to some shows and look around talk to guys who are willing to talk. Some vendors will be really cool about helping you others not so much. Just remember they are there to sell so be mindful of that and don't try to ask questions if there table is packed.