Connect the Axis to Pronterface.

Send M501 to check what your previous z-offset is set to.

In our case this was 1.0.

First layer too high, increase the Z-offset by 0.1mm.

First layer too low, decrease Z-offset by 0.1mm.

E.g. The first layer isn't sticking (it is too high) we will increase the Z-offset by 0.1mm to 1.1mm.

Enter M206 Z1.1 to set the new Z-offset.

Enter M500 to save to printer memory.