And to keep direction clear from the spotter using words like "drivers" side or "passenger" side instead of "right" or "left". The driver does not know if you are calling out your right or the drivers right
In tense situations, driver and passenger don't work. You have to rely on base instinct and no one ever giving directions says to go down the road and take the first driver turn. It just doesn't work that way. If I send you down the road and tell you to take the first right, you ALWAYS know which way to turn.
Where this gets confusing is spotters have difficulty thinking backwards. A spotter needs to react instantly with a verbal command if the driver loses focus and takes their full attention away from his hand signals and eye contact.
It's also up to the spotter to maintain control of the situation. You have to make the judgement calls as to whether or not the vehicle is staying on line and fix the situation instantly in whatever manner you deem appropriate whether it's a loud bark, or a gentle whisper.
You also have to inspire confidence in the driver so they will let you take control. More than once, I have told the driver if they don't quit watching their damn tires I will walk away and leave them to their own devices.
They don't get two chances at that. More than one stubborn person has looked up the second time from their tires to see me walking away. As the spotter, you have a large responsibility to keep the rig and driver safe. You cannot do that without their full cooperation.
The first time they do it, I stop them, walk up to the door and chat with them quietly. How many tires can you see at a time? They typically reply with the answer of 1 or 2. I quietly remind them that I can see all four, plus the obstacle, plus the line, plus the way to keep them out of trouble. Then I try again. Rarely do I have to reiterate, but when I do, they had best listen or figure it out.
I also never force spotting on folks. Some just want to do it themselves and I'm more than happy to let them do it.
In JV, another aspect of it is if I spot you into a stuck, I will stack, tug, pull, or whatever to get you out. If you ignore my spotting and get yourself stuck, I get to sit there and razz you while you get yourself out. I get you in, I'll get you out. You get you in, you get you out.
I also use very distinct and simple hand signals which are laid out and discussed ahead of time. It's very basic. You turn the direction I point, no waving, no gesticulation, just turn until I quit pointing. When I quit pointing, you hold what you got until I direct you again which I will do when it's appropriate and not until.
I do that with one hand and then control forward or reverse with the other. Forward is a come hither wave, and a straight point back is reverse. I also use a gentle palm down to slow progress.
With two hands and simple directions I can walk anyone that pays attention through a literal minefield of big boulders with few if any mistakes.
Also, I don't let a driver keep moving while I find a better vantage point where they can see me. A pair of closed fists, palms toward the driver, will halt them while I reset my position. I never let a new driver move while I find a better spot. I don't want to get run over and I don't want them to ruin the line I have them on.