Here's what you need to do to know which ones are good one's

Coin Grading:
When buying or selling collection coins, the grade is the 2nd most important factor to consider when giving a value to your coin.

A coin that is in pristine condition will sell for hundreds of dollars more than a coin that was tossed in pockets for several years.

Coin Rarery:
When you want to know the rarety of a coin, go to coin shops and look at their prices. If your coin is in a better condition than theirs, sell it for more. If you aren't sure, sell the coin on eBay and the bids will go up to the value of the coin.

Be extra careful when selling coins to not undervalue your collection. Do some adequate research before attempting to sell any coin because buyers sure are looking for a profit and will have no harsh feelings robbing you out of a precious coin for a couple dollars.