Start with serial numbers:

http://archive.gibson.com/en-us/Lifestyle/ProductSpotlight/GearAndInstruments/Gibson Serial Numbers/

Then move to the craftsmanship:

http://www.gibson.com/news-lifestyle/features/en-us/CounterfeitGibsons.aspx

You'll find even gibson can struggle with identity, but passing these first 2 tests is a big plus!