Use both sides of a paper!
How simple and direct is this tip? Always aim to decrease your use of paper and take advantage of every bit of it. If you have a printer with the double sided print option then be sure to use it. This will save you half the amount of paper that you usually use. Of course, make sure it really is necessary to print; if there is no need for a hard copy and a soft copy is just as good then simply don't print and save some paper.
P.S. Don't forget to recycle once you're done with the paper :)
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