What advice does the author of "how to jump-start a car battery" give for connecting the jumper cables to the battery? Don't start the car as you're connecting the cables. The steps listed in "how to jump-start a car battery" are organized in chronological order (from the first action to the last). When the cables are connected to the live battery don't touch the other two cables (they will spark). You must connect the cables to the dead battery first then to the live battery. The same cable must go to the "positive" and the other cable goes to the "negative" on the batteries.
Assuming that your car will permit a jump, you should be careful to prevent dangerous electric shocks. When you handle the jumper cables, be aware that their function is to transmit electrical current from one car to another.