You may have noticed that all of the print commands require you to specify a print queue. If you always print to the same printer and would prefer to not have to always specify the queue, you can set your PRINTER environment variable to specify your default queue. Then lpr, lpq, and lprm will all use that queue by default. You can always override the default by using the -P option while running these commands.
For example, to set your PRINTER environment variable in C shell (/bin/csh):
setenv PRINTER ps4
You can now run the print commands without the -P option:
lpr file.ps
lpq
lprm 123