There are many different type of holders available today. The most common type being the 2"X 2" cardboard flips. There are also vinyl 2"X 2" flips, hard plastic 2"X 2" snap shut holders as well as many other size snap shut holders. Mint issued Proof Sets will come sealed in a protective holder as shown. Some collectors prefer to keep their coins in an album with pages organized by year and mint mark. Some albums contain PVC (Polyvinyl chloride) in the plastic. This can cause irreversible damage to your coins if used for long term storage. Make sure you get a holder that does not contain PVC.
You can use single coin holders or holders that hold all of the coins minted for certain year, like shown below.
Many beginners will choose a simple cardboard folder. These are popular for circulated coins, but don't offer much in the way of protection.
When handling coins, make sure your hands are clean and be sure to only touch the edges. Oil from your skin can permanently damage the coins surface. I have seen a lot of nice uncirculated cents with an oily fingerprint ruining the surface.
Remember when choosing how to store and protect your coins, choose a holder that won't cause damage to the coin. Holders containing PVC (Polyvinyl chloride) can cause damage to your coins over time. Some 2X2 holders contain PVC. Choose instead, holders made from Mylar, which will not harm your coins. If you choose to use a coin album to store your coins in, make sure the pages do not contain PVC. If you don't know for sure, don't use it. You have a lot invested in your coins and you don't want to let them be ruined by trying to protect them. Some of the older bookshelf albums had pages that contained PVC, and many a collection was ruined because of this. You shouldn't buy the older coin albums from places like ebay. There are many new old stock piles of these albums that contain PVC being sold. They can do nothing protect your collection, but they will destroy the value of the coins you keep in them. An easy way to tell if you have your coins stored in a flip or other flexible holder that contains PVC, is to examine the coin to see if there is a greenish build up around the edge of the coin. The coin will usually appear to be stuck inside the holder, but with a little bit of flexing will slide out. That's when you will notice a greenish colored ring in the holder and see the visible damage that has been done to your coin. To test a flip or other flexible holder to see if it contains PVC, twist or bend the holder and watch for little cracks in the plastic. PVC will not crack when bent, in fact it is nearly indestructible by twisting and bending it. This is what PVC does, it makes plastic more pliable and soft.
If you already have the green film from PVC on your coins, it can be removed with acetone. Acetone will remove the film and stop further damage. To remove the film, use a soft cotton swab dipped in acetone, and roll it over the affected area. Use caution not to rub the coin when doing this. Once the film is removed, let the coin air dry. Any damage done to the coin by the PVC cannot be undone, but they do look better with the green film removed.
If you have a rare or valuable coin, one of the best ways for protection would be provided by a third party grading service. Collectors will sometimes refer to these as slabbed coins. The coins are sent to the grading service where they are graded, authenticated, and encapsulated in a special sealer holder for protection and display. Even though this may be one of the best ways to protect your coins, they can still deteriorate over time, some Copper coins, such as cents can even get ugly spots on them.
There are many third party grading services available, some of the top companies are PCGS (Professional Coin Grading Service), NGC (Numismatic Guaranty Corporation), ANACS (American Numismatic Association Certification Service), ICCS (International Coin Certification Service), and PCI (Photo Certified Institute), but there are others. The fees for encapsulating coins with a professional grading service vary, sometimes costing more than the coin is worth.
Popular slab sizes: NGC Thickness 3/8" Length 3 3/8" Width 2 3/8" (85mm X 60mm X 10mm) - PCGS Thickness 3/8" Length 3 1/4" Width 2 1/2"
Slab style holders can be purchased from many retailers, allowing you to put your own coins in them and label them yourself. These holders usually come in the same sizes as thrid party grading service holders, which makes them easy to store in custom slab boxes along with other slabbed coins