When more than one printer is available, you can specify which printer should be the default in the print dialog. Unless you choose otherwise, Mac OS X defaults to the printer most recently added. To change the default printer, follow these steps:
1. From the print dialog, choose Edit Printer List from the Printer pop-up menu.
2. Select a printer from the Printer List.
3. Choose Make Default from the Printers menu.
In the Printer List window, a gray dot marks the default printer.