Operation Lights On
The requirements for lights use are found in the AIM 4-3-23. Aircraft position lights must be on when the aircraft is operated on the surface and in-flight between sunset and sunrise. The anti-collision lights must be on during all day or night operations of the aircraft.
The AIM recommends all lights be on when the aircraft is taking or crossing an active runway. This si solely at the discretion of the PIC, though.
Most operators have specific policies on lights. The typical policies I see under Part 135 is as follows:
1. Nav lights on when power is on the aircraft (APU, GPU, or engines running).
2. Rotating beacon one when engines are running.
3. Taxi lights on when clear of the parking ramp.
4. Strobe lights on when taking or crossing an active runway.
5. All lights on for takeoff.
6. Landing or recog lights remain on until 10,000 ft HAA.