Printer ink
Printing on draft quality will make your ink last twice as long. Another sneaky trick is to use grey instead of pure black for large fonts. But do try and use thinner, smaller fonts too.
Also only print when you're sure that it's ready. Planet Ink Club's excellent environmentally friendly service refills your used cartridges for 5.99 a month, helping to save the world and print even more!
Check out the website here!