And depending on what 'long term' means, you should jackup the car. Otherwise the tires will get the whole weight of the car on the same spot and surely be out of balance after a 'long term'.
If you do what accha suggested, you should not lock the car. You won't be able to unlock it with an electronic key. So, make sure you can unlock the door manually.
Very easy. It is a 5-minute job you can do all by yourself.
Just detach one of the two cables attached to the battery of the car. For this you will need a spanner or a screw driver depending on the type of battery you have in your car. You may leave the cable lying on the battery itself but make sure the clamp is not touching anything metallic such as the bonnet (hood). You may wrap the clamp in say something like cloth just for additional safety. This will save the battery from draining out. You can re-fix the clamp and tighten it up once you wish to start the car again.