See Figure 1
Be sure that both batteries are of the same voltage. All vehicles covered by this information and most vehicles on the road today utilize a 12 volt charging system.
Be sure that both batteries are of the same polarity (have the same grounded terminal; in most cases NEGATIVE).
Be sure that the vehicles are not touching or a short circuit could occur.
On serviceable batteries, be sure the vent cap holes are not obstructed.
Do not smoke or allow sparks anywhere near the batteries.
In cold weather, make sure the battery electrolyte is not frozen. This can occur more readily in a battery that has been in a state of discharge.
Do not allow electrolyte to contact your skin or clothing.
Fig. Fig. 1: Connect the jumper cables to the batteries and engine in the order shown