Never touch or clean the surface of any coin. Coins should not be cleaned at all as doing so may end up ruining the coins numismatic value. Just touching your coins with your bare fingers is enough to cause damage to them. Your fingers contain oils and miniscule pieces of grit that will adhere to the coins and cause them to discolor or suffer microscopic scratching. When you handle your coins, wear cotton or latex gloves, and handle only the edges. Cleaning or polishing your coins will do more harm than good. Once metal has been exposed to the air, it is natural for it to oxidize, or tone. Many uncirculated and mint state coins have been ruined this way. Whenever you want to go through your coin collection, just make sure your coins are safe.
The natural tarnish of a coin is expected by collectors, and the coin will lose its value to a collector. Storing your coins in envelopes, wrapped in paper, with your notations beside the coins, or in cardboard boxes is a good way to damage them unless you are careful to use acid free paper materials. Be sure to buy only acid free paper and cardboard supplies for your coin collection. It is not a good idea to store your coins in plastic flips for longer than a few weeks, unless the flips are made of Mylar, because they can cause PVC damage to your coins. Mylar, or plastic pocket that folds in half, and is designed to hold one coin.
To protect your collection the best, store it in a dark, dry, temperature controlled environment such as a safe deposit box or specialized coin cabinet. If you store your coins in the attic or basement, you are probably exposing them to extremes of temperature and humidity cold or hot that will promote their oxidation.
Coins like the GSA CC Dollars are usually uncleaned because they have been sealed in uncirculated condition. The only sure way to know a coin has not been cleaned is to buy it certified by a reputable certification company like, PCGS, NGC, NTC, ANACS or NNC.