First, make certain your firearm is unloaded by checking the breech, barrel and magazine, if any. Store ammunition away from all firearms in a secure area. Apply a very light coat of light gun oil to the entire gun and wipe it down thoroughly. It is best, when possible, to store firearms horizontally, so oil will not run down into the buttstock and soften the wood.

Never store a firearm in a tightly sealed case. Moisture could condense and cause rust. Never leave a firearm in its case after hunting or trips to the range. Make sure it is unloaded and clean the gun as soon as possible. Make certain there is some circulation around and in the case.
It is highly recommended that firearms and other valuables be stored and kept locked in a suitable gun safe or vault.

Inspect your firearms periodically to make certain they are not loaded. Check for rust. Wipe them down again with a slightly oily cloth. Open the action and inspect the bore and barrel. Store them away from ammunition and from unwanted hands.