You've made a good move in my opinion. Start by detecting with the settings at the presets. You'll find, depending on the soil, that you'll be able to raise the sensitivity up considerably as you get used to the machine. Set the Threshold as a just audible hum. When you cross over targets that are discriminated out, the threshold will null out. I prefer hunting in the coin and jewelry mode most, but try the relic mode to see how you like that as well. Be aware that when pinpointing or hanging over a target too long that the auto ground may tune to the target and no longer beep. Locking the ground balance or keeping the coil moving will help. You don't say what coil came with it, but the coil selection available for the MXT makes it a very versatile machine. I use the 6X10 elliptical most of the time as it gives good coverage, decent depth, and good separation. The 5.3 is useful in trashy areas and the 4X6 "Shooter" is near surgical in heavy trash, but doesn't cover much area. Using headphones, I got to where I could tell the difference in sound on aluminum cans versus coins most of the time. Get out and have fun.
luvsdux