IF the light fixtures you have are the 4 bulb type, run 2 conductors, one nuetral and a ground to each light. Wire one ballast to the black and white wires, the other ballast to the red and white wires. At the supply end use a switch for the black leg and a switch for the red leg. You will be able to turn on half the wattage when you dont need "task" lighting, yet with the flip of some switches, you can double your power bill.
Lets say you want 4 lighting zones, each zone would then have 2 levels of illumination by simply running 1 more conducter and a few more switches.