How can I setup my printer to print in black and white as default?
@ughoavgfhw's answer is incomplete. Some applications (like Google Chrome) will not use the last used preset, but will use the default preset. In order to have such applications adhere to your default settings, you have to interact with the underlying printing system CUPS. These steps will get you there:


Run cupsctl WebInterface=yes using the Terminal application (only required once).
Browse to http://localhost:631/
Go to Printers
Select printer to modify
Choose Set Default Options from the second drop-down
Under Basic set Output color to Black (this step might be different for your printer)
Hit Set Default Options and presto!