as per the manual (page 491 for MY06):

Fill the fuel tank
Change the engine oil and filter
wash and dry exterior
clean the interior and make sure its all dry, no food
leave the parking brake off, put tranny in reverse (manual), or Park (auto)
block the rear wheels
leave one window open slightly if in a garage
disconnect the battery
support the wiper blades with a towel or rag so they dont stick to the window
apply silicone spray to all door and boot seals
cover the car with a breathable cover such as cotton
run the engine periodically (once a month)