There will be a lot of good advice on setting up the drone, but since the P3P is a camera foremost, these are the other preflight steps I take:
1. Observe the lighting to determine whether good footage can be produced, and the distances and altitudes the drone will have to be to find it.
2. Observe the obstacles such as trees and power lines, which may be along the intended flight path.
3. Observe where any people or animals are in relation to the flight path.
4. Consider whether there is any possibility of signal interference, such as dense trees, buildings, strong EMR, and rock outcroppings.
5. Make sure your spotter is ready and able to keep eye contact with the drone.
6. If the footage is for posting on a professional site, make sure all the owners of properties and people captured are willing to sign necessary agreements.
7. If children are present, make sure someone is available to deal with them and keep them out of the landing zone.