As you might have guessed by now, what a coin is worth is depended on many factors. Many people think that the most important factor is age. That is not the case. Valuations of coins are determined by many factors. Some include denomination, date, mint (where it was made), mintage (how many were made), wear (how close to brand new it is), and how many are estimated to survive. Just because a coin is very old doesn’t guarantee it’s rare or valuable. There are many ancient Greek and Roman coins worth less than $5 each while some coins from the 20th Century are worth millions.
Now first off you may think that after age the next important factor is its condition. Again you would be incorrect. Due to its scarcity some really ugly coins are worth a lot and some very attractive and clear coins are junk, for all intents and purposes. Coins that have been damage, cleaned, polished, or are very worn by circulation, are in general worth less than those that are not, but again, see scarcity, as talked about above.
Just as you would expect in any type of collecting, those inside the collecting world, there are many many layers to everything.
If you were to try and look up what your coin was worth, you would probably start in the “Red Book” , the bible of US Coins, compiled by Kenneth Bressett and R. S. Yeoman. There are many varieties of red books and are published almost yearly. The reason this is the bible of US coin collection is that it covers coins made by the US from start to end. It gives the estimated mintage of coins by year and mint. It also lists values.
The coin values listed are as of the date it was written, and just like any market, there are fluctuations in prices. It is a good place to start, but by no means end your search.
If you wanted a more accurate price guide, and knew what you had (which is key to reading them), then you would go to the “graysheets” or the Coin Dealer Newsletter (or CDN). These sheets are printed on a weekly basis (51 a year), in addition there are Monthly & Quarterly supplements, as well as the Greensheet (for currency) and Bluesheet (for slabs). The have the most up to date coin values available in printed form and can be found in the pockets, briefcase and tables of most if not all dealers and collectors.