I can think of five things that you need to consider/deal with. My wife and I bike to work, so we sometimes go long stretches with our car gathering dust in the garage. If we had car sharing in my area we'd probably just ditch the car - a Subaru wagon.
1. Gas - Make sure your gas cap is fairly new. That will help retain the more volatile gas fractions. However, even with that measure, your gas will break down over time. After a few days of sitting, your charcoal canister will be saturated and the remaining volatiles will just vent into the air. You might consider leaving the tank half full and making a trip to the gas station at least once a month to add a gallon. OTOH, if you're concerned about gasoline availability soon (and this might be a legitimate concern!) you could leave it full and add a gas stabilizer like Stabil.
2. A/C lubricant - If you still have A/C in this car, you are supposed to run the A/C system, either using A/C or defrost, at least once a month or so to stir up the lubricant.
3. Battery - Madpaddy covered that well. You can also use a trickle charger with the battery still in the car. As long as you hook the charger up at least a day before you use the car, and at least once a month, the battery should be ok.
4. Engine lubricant - Your cylinder walls will be mostly dry after sitting for a week. I add slick 50 to my oil because of this. Any additive with teflon or similar will help lubricate the cylinder walls when the oil has been off of them for a while. If you were going to leave the engine off for several months, you should take out the spark plugs one at a time, squirt fogging oil into each cylinder, then put the spark plug back.
5. Tires - Tires will develop a warp at the point where they rest on the ground if you leave them in one position for a while. If you're leaving the car for more than a month, you might consider putting it on blocks. It would be easier to just move the car at least a foot or so at least once a month.
So, if you're leaving it in a garage, buy a cheap trickle charger for the battery and otherwise drive the car at least once a month for a few minutes. I don't see any need to go farther than a gas station and back. Every other week or so, start it and let it run for a few minutes, running the AC and moving it a foot for the tires. If you don't have a battery charger, increase the time running the engine to charge the battery.