Nowadays the biggest enemy a person can have to learning how to find mint errors is by being on social media,
ebay etc. Unfortunately, this is where most people start.
Looking for random anomalies on coins and hoping they match up to something collectable will take you a lot more time, wasted effort, and disappointment repeatedly finding out you have nothing but post mint damage, useless
Machine Doubling,
Die Deterioration, or minor insignificant imperfections (etc.).
If you want to find real error coins the hobby values, then you need to know what to look for before hunting. Otherwise it's like trying to catch a trout without knowing what they look like, where specifically they live (lake, pond, stream etc.), what they eat, etc. The results are a lot of wasted time and effort with the ultimate result being frustration and failure.
A good way to start is, for instance, get a box of penny rolls from the bank and separate the coins by date and mint mark. Go to varietyvista.com and, date by date, use the reference there to see what errors are known for that specific coin/mint mark. Look for those specific errors/varieties using the pictures provided. After doing this for awhile you will KNOW what an actual error looks like and not have to waste time on face value and damaged coins. :)
Spend some initial time at places like error-ref.com, doubleddie.com, varietyvista.com, conecaonline.org, coppercoins.com etc. to find what actual and collectable coin errors look like.