Caring for your coins is fairly straight forward, make sure your hands are clean & dry and most importantly avoid touching the faces with bare hands as skin oils and fingerprints will tarnish them (cotton gloves opptional). Always hold them by the edges with your thumb and forefinger, remembering to keep the coin away from your breath-stream as the moisture will damage the coins face.
When holding your coins it's always a good idea to put a cloth underneath, thus avoiding scratches should you drop them. Regarding the long term storage use acryllic airtight capsules as they give great protection, and finally for optimum storage they should always be kept at a dry constant temperature.
Really important, don't forget collectors love and value the beauty of a coin in its original state, and that toning on a coin is a natural occurrence, so the value could greatly depreciate if its been cleaned.