Apple has a great article to assist you in learning how to troubleshoot printing issues in Mac OS X.
Here are some of the items they suggest.
Print a test page
If your printer has a test page feature, try to print one. If the test page does not print, turn the printer off and on then try again. Make sure the power cord is connected to a power source.
For more information on how to print a test page, review the documentation that came with your printer or look at the manufacturer's website. If printing a test page is unsuccessful, review the documentation that came with the printer for further troubleshooting steps specific to the printer.
Check cables and connections
Disconnect and reconnect every cable between the computer and the printer. Make sure all cables are firmly inserted.
- USB printers only: Switch the USB cable connection from the current USB port to another USB port.
- USB printers only: Open Apple System Profiler and click the Devices and Volumes tab. If the printer still does not appear, try a different cable.
Try to print again.
Did it work before?
If your printer previously worked with Mac OS X, continue to the next section. If not, go to "Update or reinstall printer software" below.
Delete old print jobs
Save the files you are trying to print, then delete old print jobs.
Print from another application
Try to print from another Mac OS X application, such as TextEdit. Can the issue be isolated to one application?
If the issue occurs when you try to print from a Classic application, try printing from other Classic applications, then from a Mac OS X-native application. Can the issue be isolated to one application? Does it only occur in the Classic environment?
Any time that an issue seems to be application-specific or environment-specific (Classic versus Mac OS X native), the issue could be related to either the application software or the printer drivers. Check the website of both the application developer and the printer manufacturer, and contact them if necessary.
If these don't work, take a look at the Apple article for more options.