If the bike has an alarm fitted this will drain the battery.
You have the option of disconnecting it or charging it up periodically.
The fuel in the tank will go off and will gum up the carbs so you must either drain it completely or be prepared to run the engine over for maybe ten-fifteen minutes a week.
If you do empty the tank then you have the additional problem of condensation inside it which will cause rust, which may well find its way into the fuel line/carbs.This is a major P.I.T.A
A tip here is to get your hand on some dessicators, the things that you find in many consumer goods these days, they look like small square clothlike packets.
You will need to collect quite a few of these so I’d suggest going down to your electrical retailer/shoe shop who might be generous enough to give you the ones that they usually throw away.
Warm them up on a very low oven heat to ensure they are dried out, put them in a cloth bag and hang up inside your empty tank. You will need to gently warm them up in the oven again to dry them every month or so but don’t forget the possiblility of fuel fumes, let them vent to free air for a couple of hours before drying them.
Try to find a way of supporting the bike so that it is not standing on its tyres or they may degrade forming invisible cracks in the sidewalls.
A favourite trick of many is to soak some rags in oil and put them in the exhaust pipe but make sure that you can remove them.This will prevent the baffles and exhaust rusting out.Pull out the plugs and tip in some car oil, turn the engine over preferably by hand - this will prevent the bores from rusting.Pop oily rags in the holes where the plugs were but don’t lose the suckers.
Make sure that all your cables are very well greased.
One idea to prevent the chrome and exposed metalwork corroding is to warm up some Waxoil gently so that it becomes liquid and then paint it all over and under with a paintbrush(including the mirror stalks) - sure it doesn’t look pretty but when you use an industrial jetwash to remove it you will not have to do any work to bring back that shine, indeed it may well look better than before.
Brakes are a particular nuisance, pull the pads out and pump out the pistons without going all the way out, grease them with petroleum jelly and put it all back together again.
When you put the bike back in service then you must change the brake fluid, it’s wise to change the oil.Also don’t forget to replace the fork oil.
If your bike has liquid cooling then put in a much stronger mix of antifreeze than normal, don’t empty it or the internal galleries will rust and clog up the water filter, equally you don’t want it to freeze or the engine lump will get cracked.Remember to replace the coolant when recommissioning with the manufacturers spec.
Put some good thick oil in the ignition keyhole and fuel tank keyhole or you will not be able to turn them come restart time.
Spray WD40 or similar into all the switches but make sure everything is working as it should before you finish this job.It might be a good thing to spray all the connectors including the bulb holders to prevent corrosion.
Keep the bike covered, a few old sheets wrapped around the tank to prevent frost carrying moisture in is a good idea.
You could do everything here without emptying the tank and run the engine once a week which will help to keep seals from hardening and bores from rusting.The coolant should remain highly concentrated so don’t run it for long as it will not be as effective and the engine will get hot quickly.
In fact I would prefer to run the engine rather than let it stand for a long time especially a water cooled one.(that way the water pump bearings are less likely to seize)
If you do choose to let the bike stand untouched it goes without saying that it will produce loads of blue smoke from the oil in the bores when you do restart it. Turn it over before starting to get as much out as possible.This oil will burn off quite quickly and you may have to clean up the plugs once or twice.
That covers most of it but you might go down to your dealer and ask them. You might even be allowed to park in his premises for a fee(but check your insurance)
If there’s anything I missed out I’m sure someone will fill in.