If you want to catch a rainbow trout, you need to know what a rainbow trout is.
The same with coins.
Save Yourself time, effort, and disappointment...don't learn the coin hobby backwards.
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 or useless Machine Doubling, Die Deterioration, etc.
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.
A good way to start is, for instance, separate a bunch of pennies by date. 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.
If there is a variety on a coin it will be raised on that coin. Why? Because it would be an die issue that would be incuse on the die, but raised on the coin. 99% of the incuse marks on a coin are circulation damage. Only 1% are mint errors. Just like door dings on a car in a parking lot, damage happens a lot to coin being circulated. It happens a lot. A damaged coin is thus called cull coin. Just good for spending. (But I save wheat cents then they pass by even if they are damaged. Toss it into the Wheat cent pile.