How to print to the plotter from Adobe Illustrator

When creating a new document in Adobe Illustrator, the application workspace includes two boxes, one inside the other.  The outer box represents the paper size and is dependent on the default printer settings.  In most cases, this will represent an 8.5" x 11" sheet of paper in portrait mode.  The inner box (dashed) represents the printable area of the document.  These values may be set independently in Illustrator, but in most cases, they should be dependent on each other.
Create your document at whatever size you desire.  In this example, the ruler is in inches and the figure is approximately 30" x 20".  The document size can still be seen as an 8.5" x 11" box.  The plotter holds 36" paper so your image can be as large as 34" high and about 70" long.  To make larger images, the figure must be printed in tiles.
When you are ready to print, go to the 'File' menu and select 'Document Setup'.
This will open the Document Setup Dialog box.  Make sure that the 'Use Print Setup' is checked.  Select 'Print Setup' to open the 'Print Setup' dialog box.
In the Printer section, select the dgml plotter from the list of printers.
This will open the printer drivers.  The drivers may vary between systems (Win9x, Win2K, etc.).  On the 'Paper Size' tab, select the appropriate options.  For this example, at left, the orientation is set to 'Landscape'.  Various paper sizes may be selected from the drop down list or custom page sizes may also be created.
In the paper sizes dialog box, select <custom paper size> in the 'Select a form:' drop down box.  Then define the paper size you wish to use.
Then select 'OK' to exit this dialog.
The new paper size should be shown under the 'Paper Size' tab in the printer driver properties.  Choose 'OK' until you have closed all of the dialog boxes. 
The two boxes that define the workspace should now be resized.  Occasionally, the changes do not take place immediately and it is necessary to reopen the "Document Setup" and "Print Setup" dialog boxes again; but once you close them, the changes will be in place.  Now select your entire image and place it within the inner layout box. (Remember, anything outside of the dashed box will not print!)

To print, simply choose "Print" from the "File" menu as you would in any other application, but be sure to uncheck bitmap printing.  Depending on the driver setup, a small preview of the image may show up, if it looks correct, choose "Print".

If, after setting the document size, the dashed center box does not line up where you think it should, there is a tool for positioning it.  The tool is usually located behind the hand tool and looks like a small dashed box with a cross in the bottom left corner.  Simply click and drag the box to the appropriate location.