If you're using a printer on your ethernet that's reachable by other
hosts via lpr, then you can use the documentation for standard
Linux:

  http://sunsite.unc.edu/LDP/HOWTO/Printing-HOWTO.html 
  http://sunsite.unc.edu/LDP/HOWTO/Printing-Usage-HOWTO.html 

If you're trying to use a printer over EtherTalk (the printer may be on
a localtalk wire, but you must be accessing it through your computer's
ethernet port), you can use netatalk to route lpr's requests
to it. This works for PostScript and DeskWriter printers. See
Paul DuBois' setup guide at:

  http://www.primate.wisc.edu/people/dubois/mklinux/ 

If you're trying to use LocalTalk (the skinny wire sticking into your
printer serial port), forget it -- neither Mac port supports the LocalTalk
wire protocol. Apparently getting the port configuration and timing right
is really tricky.

jonh@cs.dartmouth.edu