Most equipment trucks are usually no higher than 12 ft., 6 in., and most telephone or electrical wires are no lower than 13 ft., 6 in., but this is not written in stone: “Measure it safely.”
Listen like a field mouse, but be ready to spring like a leopard when needed. This proves two things: (1) You are paying attention (good for points), and (2) you can anticipate what is needed (better for call-backs). Trust me on this. This practice works for any profession.
Play the sag load (that is, the weight of the light unit that is being rigged) when you rig. Add a little extra pull, then let it sag into place.
Sometimes the key grip is considered the unofficial safety expert.