Proper connection order first, details below.

For JUMP STARTING with 2 vehicles:

1. Red jumper to positive (red +) of dead battery.
2. Red jumper to positive (red +) of charged battery.
3. Black jumper to negative (black -) of charged battery.
4. Black jumper to dead car’s frame (engine bolt) – NOT negative terminal of dead battery.
   Keeps final connection spark away from the dead battery.
5. Charge for 3-5 minutes.
6. Start the dead car.
7. Disconnect in reverse. #4, #3, #2, #1.

For INSTALLING a car battery:

1. Red cable to positive (red +) terminal (wrench to frame does nothing – no circuit to connect).
2. Black cable to negative (black -) terminal (wrench to frame does nothing – negative to negative).

For REMOVING a car battery:

1. NEGATIVE (black -) terminal first (wrench to frame does nothing – negative to negative).
2. Positive (red +) terminal second (wrench to frame does nothing – no circuit to connect).

Explanation of safety.

For jump starting – this method avoids arcing between cars and/or terminals and watches out for sparks when completing the circuit’s final connection which could ignite fumes around a lead-acid dead battery that might be leaking. The last connection in the circuit usually causes a spark so we (who know about electronics and circuits) don’t want that final connection to cause an explosion. The chances of an explosion are low – especially if you are outside and there is enough wind to blow fumes away. We have to mention the possibility of explosion because the gasses produced by lead-acid batteries can ignite from a spark. In some newer cars, jump terminals are available under the hood and batteries are stored in the trunk or wheel wells to increase distance away from jumper cable sparks.

For car battery assembly/disassembly – these methods are used to avoid the potential differences across the terminals of batteries and your metal (conductive) wrench and the car frame. We want to avoid making a circuit in any circumstance where the wrench is connected to a terminal while tightening the bolts.

I wrote this post because the internet is riddled with frustratingly, infuriatingly, annoyingly incomplete answers which only confuse people. Some are so detailed that the answer is buried in the post. Others talk about one without the others and can mislead people easily. This post has the most common answers first at the top of the post, and all in a single place. With only a brief explanation as a reminder.

I needed this.