In most cases, the best answer is do not clean coins. While you might think they'll look nicer if shiny, collectors prefer coins with an original appearance. Cleaning a coin may reduce its collector value by half or more.
Cleaning coins is similar to restoring works of art - they're both jobs best left to professionals who have the knowledge and experience to know when it's advisable, what techniques will work best and how to use them properly.
Never abrasively clean coins. Even wiping with a soft cloth will cause small but undesirable scratches, which will reduce the coin's value. If the surface of a coin appears to be tarnished, it is best left alone as the colour change is the result of a natural process, which collectors call toning, and this natural toning sometimes increases the value of a coin – especially when it is considered attractive.
How should I store my coins?
Ask a coin dealer for advice on what would be the best option for your collection.
Environment - A relatively constant, moderate temperature and low humidity are preferable for long-term storage of coin collections. Placing packets of silica gel in the coin storage areas also helps to control atmospheric moisture.
Containers- Several types of "containers" for coins are available. Most anything will do for coins with little numismatic value, while nearly airtight holders made of inert materials are a good idea for valuable coins.
Bags, jars and boxes are adequate for pocket change and circulated bullion coins.
Paper envelopes of various sizes are sometimes used for one or more coins. Be sure to use envelopes made specifically for holding coins or, in time, your coins may change colour (natural toning) because of a reaction with sulphur or other chemicals present in the paper.
Folders and albums are sold for series and type sets and when properly used, they offer some protection from wear and handling but, if thus stored for several years, coins may develop natural toning.
Mylar-lined cardboard, often called "2x2s" but also available in other sizes, are similar to plastic flips. A coin is placed between the two halves, which are then stapled together.
Tubes are plastic containers designed to hold a number of the same size coins and they are fine for bulk storage of circulated coins and can also be used for higher-grade coins, provided the coins do not move. A distinct disadvantage is that the coins cannot be viewed without being removed from the tube.