You actually use a different command to print depending on which spooling software you use.
Most systems today ship with lpd, so this section won't apply. That said, I now recommend that people install and use PDQ in most cases instead of (or in addition to) lpd. PDQ just has much better support for printer options and such.
With PDQ, instead of the lpr command, you use the command pdq or xpdq. Both work much like the traditional lpr in that they will print the files you specify, or stdin if no files are given.
Xpdq is an X Windows application that shows a list of available printers and a summary of the print queue (including current and historical jobs). There are two options under the File menu, one to print specific files, and one to print stdin. You can set whatever options are defined in your printer driver from the Driver Options dialog; typically there will be duplex, resolution, paper type and size settings, and so forth.
The PDQ system's command-line printing command is simply called pdq.
It can be used in place of the lpr command in most situations; it
accepts the -P printer specification argument. Like lpr, it
prints either the listed file(s) or stdin.
Printer options can be controlled with the -o and -a
options.
If you've already got lpd setup to print to your printer, or your system administrator already did so, or your vendor did so for you, then all you need to do is learn how to use the lpr command. The Printing Usage HOWTO covers this, and a few other queue manipulation commands you should probably know. Or just read the lpr(1) man page.
If, however, you have a new system or new printer, then you'll have to set up printing services one way or another before you can print. Read on!