Check out the eBook, starting on page 10. But to reiterate briefly, Noise Cancel first, set the Sensitivity second and Ground Balance third. Then, before you start the hunt, go back to the Sensitivity and raise it to a point where it is just shy of chattering.
You do not have to change the ground balance when you switch to All Metal or another Pattern. But it is a good idea to check your ground balance frequently during your hunt. And always check your ground balance when you switch coils.
In more detail......I always run my Volume full bore on my 705, so I don't have to worry about changing it. In addition, I run my Threshold at 4 or 5 (depending on which headphones I am using), so I don't need to adjust that each time I hunt. I typically run with zero discrimination and multiple tones, so I don't need to change either of those. Since I have set Pattern 4 up as zero discrimination, the 705 starts up with that mode. These settings are the same for each of my coils. So basically, that leaves Noise Cancel, Sensitivity and Ground Balance. Once it is turned on and I've checked my batteries, I hold the coil parallel to the ground, about 18-inches in the air, and do an Auto Noise Cancel. Next I raise the Sensitivity to a level that is between max and mid-point. Then do an Auto Ground Balance over a spot that is free of metalic objects. After properly ground balancing, raise the Sensitivity to a point that maximizes the potential of the detector without creating false signals when you sweep the coil. For those who don't have the Auto features on their X-TERRAs or are not familiar with the audio responses made in ground balancing, I recommend lowering the sensitivity to the mid-point before ground balancing. (Just as running with a Threshold too loud, having too high of Sensitivity setting can interfere with hearing the tones of ground balance). After you do a proper ground balance, raise the Sensitivity to a level that doesn't cause chatter or false signals when sweeping. For those using the 70 or 705, you can eliminate doing a ground balance by switching to Tracking, sweep a few seconds, then lock in the new ground phase setting by taking it out of Tracking.
JMHO HH Randy