I recently went on a trip and spotted for several vehicles. I am confident in my spotting ability but the in order for success, the driver must follow the directions of the spotter. It's important that the spotter communicate, ahead of time, the signals which will be used.
Keep in mind:
Signalling the driver to come forward doesn't mean turn your wheels!
Signalling to turn your wheels doesn't mean forward or reverse!
You get the point?!