As VRWagZ1 says, the correct way to jump start is NOT to directly connect the negative terminals of both batteries:
1. Position the two vehicles so that they are NOT touching and apply the park brakes. Automatic transmission are to be placed in PARK and manual transmissions placed in NEUTRAL. Turn 'OFF' the ignition, lights and all other electrical loads.
NOTE: Ensure that booster vehicle's battery has a 12 volt rating and has negative earth connection, otherwise serious injury or damage to electrical equipment may result.
2. On both batteries, check that vent caps are tight.
3. Attach one end of one jumper cable (red) to the positive terminal of the booster battery and the other end of the same cable to the positive terminal of the discharged battery.
4. Attach one end of the second jumper cable (black) to the negative terminal of the booster battery and the other end to a solid stationary, metallic point on the engine of the vehicle with the discharged battery. DO NOT CONNECT DIRECTLY TO NEGATIVE POST OF DISCHARGED BATTERY.
5. After making all connections, ensure that jumper cables are not on or near drive pulleys, cooling fans or other points that will move when the engine is started.
6. Start the engine in the vehicle with the booster battery and run the engine at a moderate speed for a few minutes.
7. Start the engine in the vehicle with the discharged battery. Once engine starts, allow both engines to idle for approximately five to ten minutes (this allows both vehicles electrical systems to balance) and then leave running and remove the jumper cables by reversing the installation sequence. When removing each clamp, take care that it does not touch any other metal while the other end remains attached.
NOTE: If engine in the vehicle with discharged battery does not start within 30 seconds, stop cranking the engine and check for cause of engine not starting.