Most of us know that we should use black ink only when possible to save on our color cartridges. Some of us take them to office supply stores to refill or recycle. Some of us may have even attempted to refill them ourselves (I do my own black, but not color!!)
Another idea though: get to know your printer and it's options. Printers now come with several printing options - mine has FIVE different settings for the ink usage (print quality). I use "fast draft" for most of the stuff I print (coupons, recipes, etc.) and save the Maximum DPI for pictures and Papers (for school). Using the fast draft will not only saves ink, but it saves time too - it prints VERY fast!