How can I tell what tuning a song is in besides obvious ones like standard. I mean like the difference between drop c and half step down, to drop d, to even tell differences between drop c#, etc

Any theory behind this, to confirm what tuning any song is actually in! Thanks again!
I'm talking about the really hard ones to differentiate from, the songs that don't give many clues such as bass notes, etc
Schechter Hellraiser C-1 FR
Line 6 Pocket POD
Fender 15G Amp (Boo)
ESP Signature (Syu) Crying Star
ESP Signature (Leda) Horizon II NT
Marshall DSL100 Halfstack
BOSS GT-10 Effects Pedal
There is theory to some degree, but not too much. It's more intuitive than anything. The key of the song might tell you a bit, but there's no guarantee. Just listen to the song and figure out the chords. That will give you a better idea of the tunings.
Quote by Geldin
Junior's usually at least a little terse, but he knows his stuff. I've always read his posts in a grouchy grandfather voice, a grouchy grandfather with a huge stiffy for alternate picking.
Besides that, he's right this time. As usual.