Purchasing Kennedy half dollars in mint condition should be your goal, since the state of a coin is really important to its worth as a collectible. Any coin which is damaged, marked, scratched, or scuffed will usually suffer a serious reduction in value compared to a coin in finer form. Collectors should consider more than just a coin's age to determine its value. Of course age and rarity make a coin more valuable to collectors, but they aren't the only factors that matter. When thinking about market value for a particular coin, always try to assess the demand.
It‘s best to avoid handling coins if you can. The condition of collectible coins impacts the value: dirty, scratched, moisture-damaged or otherwise imperfect coins can result from too much handling. When it's absolutely necessary you should hold them on the edges.
Cleaning coins is not recommended and if necessary should be left to an expert. Removing a coin's slowly developed patina might make it less tempting to collectors and possibly less valuable.
Although the majority of coin collection holders will store your Kennedy half dollars safely, be sure that the really valuable items in your collection are safe from moisture as well as just fingerprints and dust. While packets that are held by staples or tape don’t give the greatest protection, there are alternative bags available that can block moisture as well. In any case, it is best to store collectible coins in a dry place; never store them in a basement or other cool, damp area.