
To start with you probably need to purchase a copy of the
Red Book on coins by Whitman Publishing. That book would allow you to get a little better idea of what you doing and looking for.
Unfortuately there is more than just the coins appearance to consider. Also, you may want to get familiar with error types since you could be getting rid of a valuable coin due to having one already. Not realizing the one you don't want is worth much more due to an error in minting.
A well worn coin could also be a valuable coin. A dirty coin too could be one of great value. For example a 1972
Lincoln Cent that is dirty but doubled could be worth many hundreds of dollars more than a bright shinning normal one.
Now here is the worst part of what your doing. If in fact those folders are the ones where you push the coins into a slot, no reverse is visible, those are not to great for coins. You push the coins in with your finger or thumb. Some people even use a rubber hammer. Your fingers leave oils and acids on the coins. The inside of the slots are full of glue from the manufacturing process.
Possibly not now but consider in the near future looking into the purchasing of what is called Coin Albums.