The best way to get better is to do it! Discussion groups can be helpful because you learn not just how to identify symbols or pick up on them but also when somebody may be "reaching" a bit or seeing stuff that isn't there.    I'm not particularly great either, I've just taken a lot of English courses. Shakespeare is hard as hell for me to read and I can   only really understand what was going on by asking the people around me.     Even if you don't want to read there are some good TV shows out there that can do symbolism well. Legion on FX tells a lot of things through symbolism, it's one of my favorite shows.    If you like comics The Watchmen has great symbolism and framing. As does V for Vendetta. The Sandman comics are good, too. I also recommend Ichi the Killer if you are feeling adventurous. It is definitely NSFW/L depending on your views. Ichi is one piece of work I try to get other people to read because I still have some serious unanswered questions about things.    If you are into any other kind of media let me know, I'd be up to try to find some good examples of works that use heavy symbolism.