The best place is where the cable from the neg post attaches to the engine or frame. Unfortunately that's quite often on the engine near the fan, which is a hazard to cables and hands. When you hook the cables up the engine's not running, but hopefully it will be when you're done. It also helps if the car doing the jumping, is running.
One other caution. Some older foreign cars are POSITIVE GROUND. It's rare, and if you have one you're probably aware of it. BUT, if someone offers you a jump, be aware of their car.
