Setting up printers in OS X is generally fairly simple and straightforward; however, in some instances people have found that after upgrading their systems or otherwise modifying their setups, their printers have stopped working properly. In some instances bugs in a software update can cause problems, as was the case with the OS X 10.6.8 update causing print jobs to pause, but at other times the problem may lie in the printing system's configuration.
The most effective way to address an inability to print will depend on the nature and extent of the problem. If the issue is a bug in Apple's software then generally you will need to downgrade your system or wait for a fix to be issued by Apple; however, if it is a configuration problem then you can usually resolve the issue by resetting the configuration and setting up the printing system from scratch, or trying third-party drivers and configuration options.
Downgrading your OS or waiting for a system patch can be a hassle, so a printing-system reset may be the easiest initial approach.
To reset your print settings, open the Print & Fax (or Print & Scan in Lion) system preferences. Then right-click the list of printers and choose the option to reset the printing system (it's the only option). After you confirm this is what you want to do, the printers in the list will be removed.
After the printers are removed, you can add them again either by using Apple's supplied drivers or by using a third-party driver, if one is provided by your printer's manufacturer. To use Apple's drivers, click the plus button at the bottom of the printer list to add your printer. Select your printer in the list and ensure that the driver being used is the appropriate one for your model of printer.
If the driver says "Generic PostScript Driver" when installed, then click the menu containing this name and choose "Select Printer Software" and then locate your printer on the list. If your printer is not on this list, then you can try using the Generic PostScript Driver or try a printer model that is similar to yours. For instance, if the list contains model 3000 and yours is model 3005, then you can try the model 3000 driver to see if it will work, as the differences between them could be minimal enough for it to print successfully. You may also see multiple driver versions on the list for your specific printer, namely labeled CUPS and another labeled Gutenprint, so you can try either of these to see if one works if the other does not.
An alternative approach is to avoid Apple's driver set and try installing a third-party driver from your printer's manufacturer, if one is available that has been tested with your OS version. To use this driver, with the printing system reset and your printer list cleared, download its installer and run it with your printer attached to your system and turned on, and the driver installer should set it up properly.
If you cannot get your printer to work regardless of what driver you use and after resetting the printing system, then your best bet may be to downgrade your system until an update or alternative fix is released to address the issue. This is especially true if the printing problems began happening immediately after a system update. To downgrade your system, you will need to have a recent full-system backup such as a Time Machine backup, or a system clone; it's recommended to make such a backup before any system update, no matter how trivial.
For Time Machine, boot to the OS X recovery drive (or your OS installation disc) and then select the option to restore from a Time Machine backup, which may be available from the Utilities menu. From here, select the last backup that was created before you updated your system, and restore that to your hard drive, then reboot your system.
To restore a system clone, boot to the clone disk (restart and hold the Option key to select it from the boot menu), and then use your cloning tool to clone the current boot disk back to the internal drive. Before doing this you may need to format the drive, which you can do either with Disk Utility or with your cloning tool if it supports this option.