It would be better to, weekly, start it up, let it warm up to operating
temp, and drive it a short distance.

Otherwise:
1) FILL the tank with gas, to the top of the filler tube.  Less air =
less oxidation in the tank

2) REMOVE the battery from the vehicle entirely.  This will reduce
corrosion in the engine compartment.

3) LIFT if at all possible, put the vehicle up in the air, using jack
stands under the rear axle and front lift points, or just using all lift
points.  It only has to be an inch.  This helps with both suspension and
with discouraging critters like mice.

4) MOTHBALLS in the cab and engine compartment, keeps away the mice and
squirrels

5) GREASE everything, hinges, locks, etc, and consider greasing the
front rotors, keeping in mind the grease will have to be cleaned off
with brake cleaner to drive it.  Otherwise, a year of oxidation on the
rotors may be more than just driving can scrape off

6) BED - make sure that water can drain from the bed, to prevent rust

7) OIL - a fresh oil change is better than a used oil change for storage.

and any other things you can think of: remove the stereo if it is a
fancier model, consider a tarp cover, etc etc.

When starting it up from storage, remember to clean the rotors if you
greased them, regrease everything else, pull the spark plugs and throw a
few drops of oil in each cylinder, pull the ignitor and let the engine
crank a bit without starting, etc etc.

good luck,
GTr

The best thing to do is either sell it OR drive it 20 miles
a week, every week.  1500 miles a year, if done right is all you
need to keep the car properly running.

Oh - every 3-4 months, take out out on the weekend and run it
like you normally would.  Get some highway miles on it
once in a while to get rid of the crud.

Good tips by others, and they are not wrong.

I'd fill the gas, change the oil and disconnect the battery.  That's it.

New England in the weather?  Rent a garage.  A plug in to run a SMALL
dehumidifier is a plus.

If rust has set in, seriously consider selling it now.  After three years,
I'd order a new Tacoma Limited.  Extended Cab or Double Cab is her choice.

 I'd sell it if she knows she probably won't be back for 3 years.  If you
don't, you may be paying insurance and license fees in order to run it on
the road.  You'll have to keep the gas fresh, and you don't know what could
be going wrong just sitting there.  Anything from paint and tire damage
because of sun exposure to fire to rodent damage can occur, and a new
battery is very probable.
 If it's a military assignment, she may be able to take the car with her.
And she can probably buy a new one while over there and pick it up in the
states.

Thank you all for your responses!  She will have lots to think about,
like whether or not she really wants to hand the keys of her new
Tacoma (extended cab) over to her mom and dad to trek around in.  I
have archived your posts to refer to and will let her decide what she
thinks is best.  (I have been wondering how well that Tacoma would
work at yanking out old tree stumps from the backyard.  The task blew
out the front differential on my old 1969 Jeep CJ5... Just kidding, I
wouldn't really do that...)

Ender

"The only thing necessary for the triumph of evil is for good men to do nothing."  Edmund Burke