Winterizing
The GS500, like all motorcycles, should not sit for long periods of time without use. Failure to properly prepare the bike for long term (2+ month) storage can result in problems with with fuel system, battery, tires and finish of your motorcycle. If possible, running the engine periodically (once in 2-3 weeks for 15 minutes) can minimize the negative effects of sitting.
General Long Term Storage
Gasoline. If you intend to store your bike for an extended period of time, it is highly recommended that you either drain your fuel tank, lines, and carburetors, or add a stabilizer to your fuel. Stabilizer can be purchased from many motorcycle stores and will keep sediment from building inside the float bowls in your carburetors. Highly recommended fuel additive (which does a dozen good things besides stabilizing fuel) is called SeaFoam. Over the course of winter sediment can build up that you will need to remove the carburetors and clean them by hand, a tedious and somewhat complex process. If you don't drain the fuel then keep the gas tank chok-full with treated gas to avoid internal tank rusting.
Battery. Disconnect the battery and remove it from the bike. Check and correct the electrolyte level. Keep the battery in a cool place (but not in contact with cement/concrete floor), fully charged, preferably connected to a trickle charger (if not, before riding again you may have to recharge the battery).
Tires. It's best to set the bike on the center stand and slightly lift the front wheel off the ground by putting something like a jack stand/wooden block/etc. under the engine case. Make sure both wheels are off the ground. This way you will avoid developing flat spots on the tires due to prolonged single-spot contact with the pavement.
Winterizing
If possible, store your motorcycle inside in a heated or neutral temperature area to minimize the effects of excessive heating and cooling. If no such area is available cover your bike well and try to keep away from heavy snow or other precipitation.
Reviving the GS500
After your GS500 has been stored for a while it will be necessary to perform some general maintenance before safe riding. Reinstall the battery, if it was removed. Check the chain and make sure it is within specifications. Refill the tires to optimal pressure. Check the oil level. Finally, check the electrical system including headlight, turn signals, and brake light.