What is the correct way to put a set of tires and wheels in storage??

Please note--the tire and rim setup i have is only used for mud running but i wasnt sure how to store them.Rims are just a set of rusty extras for the mud but the tires are in excellent condiditon.Should i keep them upright,layed flat,with or without air in the tires etc etc.I just dont want them to go bad while stored.Thanks.|||Up, down, sideways, it doesn't matter. Air pressure at what you normally run them and check the pressure when you take them out of storage. If your storing them for a long time, wipe them rubber down with armor-all or some other protectant against dry rot and fill the tires with nitrogen if you want to go to the expense.|||Keep them pressurized if you dont then the rubber will crack when you re-inflate them.