The effects of 2-3 months of storage are benign. To play it safe, though, here are the things that I do when I used to store my Stang every winter (4 months or more) before moving south:
1. Stablizer in the fuel tank, car driven at least 20 miles to get treated fuel throughout the fuel system.
2. Relatively fresh oil change (if using synthetic blend, no more than 3 months prior to storage; if using full synthetic then no more than 8-9 months prior to storage).
3. If your battery worries you, either disconnect it or connect a Battery Tender (or any other brand) trickle charger
4. If rodents are a concern, stuff wadded steel wool or aluminum foil in the tailpipe and intake openings (just be sure to remove later!)
5. Place cardboard, carpet or some other vapor barrier under each tire or jack up as mentioned earlier
6. If you want the cabin to smeel nice after storage, place a scented dryer sheet or other "smelly" air freshener in the cabin
Starting the car and letting it run at a standstill is more detrimental than not starting it at all. If it's to be started, it should also be driven at least 20 miles to drive off moisture and to get the seals heated up.