when jumping a car which cable goes on first

When jumping a car, the proper order of connecting the cables is as follows:

1. Connect one end of the red (positive) cable to the positive terminal of the dead battery (the car that won't start).
2. Connect the other end of the red (positive) cable to the positive terminal of the good battery (the assisting car).
3. Connect one end of the black (negative) cable to the negative terminal of the good battery.
4. Connect the other end of the black (negative) cable to a solid, unpainted metal part of the dead car's engine block or chassis (a good earth point), not directly to the negative terminal of the dead battery.

This sequence is important for safety reasons, mainly to avoid sparks near the dead battery which could cause damage or ignite hydrogen gas potentially emitted by the battery. After connecting the cables in this order, start the car with the good battery first, then attempt to start the car with the dead battery. Once the dead car starts, remove the cables in the reverse order. In summary, the first cable to connect is the red positive cable to the dead battery's positive terminal. This procedure is recommended to minimize the risk of sparking and ensure a safe jump start.