This is the guide by J.T. Stanton that got me started on how to distinguish
Machine Doubling,
Die Deterioration Doubling, and doubled dies:
https://www.jimscoins.com/downloads...%20Flyer.pdfThe articles on the Wexler site about minting technology, die manufacture, and coin striking are also a great place to learn about various kinds of doubling.
One quick mental test you can use is that doubling is unique to a die. It almost never happens that a doubled die obverse ends up paired with a doubled die reverse. The same with repunched mint marks. If you have a coin with doubling on both faces, it's likely
DDD or MD. If you have a pre-1987 American coin with doubling on both the devices and the mint mark, it is also very likely to be
DDD or MD.