This option is VERY IMPORTANT. Under the Label Utilities menu select "Show Printable Area". A dotted line will appear on your label in the label screen. Make sure all the fields that are turned on appear inside this dotted line. Anything appearing outside of the dotted line WILL NOT PRINT.
To allow for maximum print space, if you are using a Laserwriter be sure you have "Larger print area" checked, and if you are using an Imagewriter you have "No gaps between pages" checked.