There are many things to consider when investing in coins. There are volumes written on the subject but this will touch on a few items. One thing to remember is if you are interested in collecting and investing: Buy the book before you buy the coin.
VALUES: Coin values vary from day to day similar to bullion. Their values are determined by various attributes such as market values from dealers, collectors, auctions, coin societies, and sellers. These values will vary by type of coin, grade, availability, and rarity.
RARE: Rarity of a coin is determined mostly by how many there are out there. The older a coin is usually will show rarity if that coin is in good condition. There are those coins that have sold for millions of dollars because of said rarity.
STORAGE: Safety is paramount for storage. A good safe is required for the collector. Also, the individual storage of a coin is important. DO NOT SKIMP when it comes to storage. For instance: PVC or polyvinylchloride is in various holders available for coins. PVC will damage your coins. The coins stored in PVC will incur a greenish hue that actually adheres to the coin and will decrease its value. Always use archive quality holders, flips, tubes, albums, and boxes for the safe storage of your coins.
CLEANING: NEVER EVER clean your coins. Every time, amateur cleaned coins will drop the coin’s value dramatically. In the event that a coin has become damage environmentally as in a fire or flood, these coins can usually be repaired and preserved by a professional cleaning service usually for a fee.
GRADING: Another subject that books have been written about is grading. The current grading scale is the Sheldon Scale devised by William H. Sheldon. This scale has a numerical value of coins ranging from 1-70 with 1 being the lowest and 70 being perfect.