Setting it up
The plotter is an HP DesignJet 300. It is connected to the network using an HP JetDirect EX interface. The printserver's IP address is 10.13.0.50. Please don't change the printserver's IP address or configuration, it is not at fault.
With a Mac Not sure about Macs. Based upon what's in the Use the Printer HOWTO, this seems pretty straightforward. Just know that "port 9100" is the protocol to use, and if it gives you a choice between PS and HPGL, use HPGL.
With Windows On a Windows box, you need to ignore the temptation to click "add a network printer", and instead, "add a local printer", then "create a new port", then port type "standard tcp/ip port", then enter 10.13.0.50, and everything else should be sensible.
Since this is an older plotter, HP is no longer writing the drivers for Vista and later versions of Windows. However, there is a set of drivers available for Vista and Windows 7 here: http://www.mediafire.com/?njmtmnizmjm Use them at your own risk!
How Much Does it Cost? The cheapest HP plotter paper is about $0.15 a foot. Throw some money in one of the jars when you're done. :)
When You're Done
Before you walk away, make sure that the printhead is "parked" on the left side. If an error occurs during plotting, it will sometimes stay out over the paper. Leaving it this way will allow the printhead to dry out and clog. To check, just lift the hood from the center and see if the printhead is over in the well on the left side. If not, power-cycle the plotter and it will both clear the error and park the printhead.
For More Information
The user manual for the printer is available here: http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/bpp02419/bpp02419.pdf