Disconnect battery, grease terminals.

Run some fuel with stabilizer in it. Drive through half of a tank to make sure it circulates through the system, and then fill it up and add more stabilizer to the rest of the mix.

Change oil a few hundred miles before putting it away. In fact, change anything that is getting old, even antifreeze.

Wax the paint and spray polish or spray wax on the rims.

Blast anything on the underside that looks like it MIGHT rust with black rust preventative paint or undercoating (obviously not the exhaust)

If you can park it in one spot (inside):

Best: Park on wheelstands, stack rims. Or well-placed jackstands.

2nd: Park on a piece of plywood for each tire (avoids dry rot/cracking).

You CAN cover it but if it's inside it isn't that big of a deal.

If you park either inside or outside:

Treat the leather and cover the seats with old sheets or towels. Ditto the dash. Use white towels or sheets (obviously if you arent covering the whole car).

I like to cover the air intake with a piece of screen so that little critters stay out of there.

Have a new distributor cap and rotor ready for when you get back.

--I know it sounds like a lot to do but it really doesn't take that long.

Best of luck to you.