There are a few things that we recommend to do when preparing your car or truck for long term storage:

Top off the fluid levels. A full reservoir will leave no space for condensation to occur.
Change the pol and filter. Old oil will become acidic and eat away the inside of your engine. Fresh oil takes longer to break down.
Grease steering and suspension. A full grease service will keep the seals and rubber bushings from drying out.
Top off the fuel and add a fuel stabilizer. This will keep the gas from breaking down and evaporating.
Older vehicles disconnect the battery. With newer vehicles, you need to leave the battery connected or else the computer will need to be reprogrammed.
Never engage the parking brake. The brake pads can rust to the rotor or the drum and cause the wheel to seize. Use wheel chocks instead.
Esnure all windows are closed and the vehicle is locked.