Printing in draft uses much less ink or toner
Print in draft mode where possible
The thought of printing every page at the best quality might be alluring, but it is costly and often unnecessary. You may need to print presentation documents at a high setting to impress clients, but stick to lower quality settings for circulation around the office or personal reference.
The range of quality between the lowest and highest quality settings differs from printer to printer; where some produce messy and almost unreadable documents at draft, others are only slightly less accurate than their best quality counterparts. You might need to experiment, but you can almost certainly stick with draft settings in almost all cases. This will also certainly lengthen the life of the ink cartridge or toner.
"Toner Save" mode doesn't always degrade print quality
The same goes for "Toner Saver" modes on laser printers and multifunctions. In some cases, this mode can be used in conjunction with a draft or low-resolution mode to produce readable documents that don't use excessive amounts of toner powder. Again, ensure that your particular printer implements this mode without sacrificing document quality, but in most cases this should lengthen your toner's life.
Watch out for automatic settings
Some printers are stubborn; you might select a certain quality setting or print mode but it won't always stay that way. Be sure to check the advanced printer settings every time you print a document to ensure your desired settings haven't been overwritten. With many printers and multifunctions, you might find the settings have automatically reverted to default settings, including quality and whether or not "Toner Save" has been enabled or not.