Printers use either ink cartridges or toner cartridges, depending on whether they are an inkjet printer or laser printer. Both of these types of cartridges need to be refilled when they run low. Some printers don't give any warning before they run out of ink, some give a "low ink" warning and others will stop working before they run out of ink. You will be forced to replace cartridges even if you can see ink inside. However, a little sticky tape in the right spot can help keep your print job running long enough to get that last essay or letter printed.
Open your printer and find the ink cartridge.
Remove the cartridge according to the instructions in the printer's user manual. Gently rock the cartridge from side to side to get as much of the ink to the bottom as possible.
Replace the cartridge, close the printer and try printing.
Open your printer and take out the ink cartridge.
Find the sensors on either side of the cartridge. These will look like two small holes.
Cut pieces of the electrical tape that are large enough to cover the holes. Stick the pieces of tape over the holes so the tape is smooth and doesn't get in the way of the cartridge's operation.
Replace the cartridge and try printing.
You can use white labels or any other thin, opaque sticky material to cover the sensors. Try changing your printing preferences to "Draft." This uses less ink and might let you get out some more pages.
Some manufacturers say that allowing a cartridge to run out of ink can harm the printer.