Hi Jerry - Regarding XYZ
Z's easy, universally +Z is up and -Z is down (I think). Now X & Y just have to follow the right hand screw rule. I use a laptop on my machines and I orient the X&Y in the same orientation as UCCNC has it on the screen so its WYSIWYG. This means it's different on two machines because on one I have the laptop facing the machine and on the other its to the side of the machine. So its up to you. But convention has it that standing at the front of the machine as Pippin says X positive is to the left, Y negative is away from you and Z positive is up. Peter