Threshold should be at a just barely audible level. I set mine with the coil waist high, before GBing. The other three things you asked about are all part of an actual hunt. Therefore, the coil will be skimming the ground when they come into play. I like to run my Sensitivity as hot as I can without creating false signals. During the course of a hunt, I may raise the Sensitivity level in areas with few targets or lower the Sensitivity level when the ground becomes congested with multiple targets in each sweep. TID stability only comes into play when a target is located. If you are hunting in highly mineralized ground and want to use the TID Stability, once you set it, you can leave it on during the course of the hunt. Personally, I don't use it because I don't hunt in areas of highly mineralized soil. Tracking ground balance is based on how the X-Terra reads the ground and will take care of itself as you sweep the coil. JMHO HH Randy