Paper in either a rectangle or square in a desired size (warning: if paper used is not one of these two shapes, the instructions will not work).
Step 1: Making a perfect square.
2. Fold one corner of the paper to form a 90 degree triangle, going all the way to the edge of the paper (see figure 1).
3. Cut or fold and tear off the bottom segment (see figure 2).
4. Unfold the triangle and do your best to remove the crease by rubbing your thumb along the paper. (see figure 3)