Communication between spotter and driver is key to a safe and successful winching operation. This helpful overview from Warn Industries outlines the proper hand signals to use when winching. Share with your buddies before your next outing so you don't have to yell back and forth; possibly waking the sleeping bear right next to the trail.
When spotting a vehicle that has to reverse out of a situation and line of sight with the driver is not possible, ie. when the spotter is on the rear portion of truck, we have found that the best and most consistent verbal cues for steering are to use the terms, "right hand down" or "left hand down" to convey which direction to steer the vehicle. These simple verbal cues leave no room for guessing on which direction the steering wheel should be turned.
Have fun, be safe, and Keep Exploring!