Cover up every single entry point into the cabin and engine with
wire mesh to keep the rats out.
Rats got into my car several years ago and ate the plastic steering wheel.

Change the fluids, adding appropriate fuel stabiliser and cylinder lube
through the plug holes, as instructed by the product information. Block all
holes, such as exhaust, inlet etc.
Remove battery, wheels and tyres and use a removable rust preventative on
discs etc. Make it rodent proof by blocking air vents etc. Bait the
surrounding area with rat poison, being careful to protect it from children
and cats, on a regular basis.
Put it away dry and make sure there is some ventilation.
Best to keep it in a dark place for the sake of rubber bits.

You will need to do some preparation before taking it out of storage too.

Huw

In addition to everything everyone else said, I would put the car up on
blocks, too.  Putting extra oil in the crankcase (to prevent rust) is a
good idea, too, in my opinion, as is storing it with a full gas tank (it
can't rust that way).