Fold a standard piece of printer paper in half vertically and crease.
Open up the paper so that the crease is vertical and fold the top two outer corners inwards so that they meet along the middle.
Fold the point made in the previous step down to the crease so that the flaps are tucked under this fold. Now the paper should look somewhat like the back of an envelope.
Fold the two top corners created in the previous step to the center crease so that the points are about 2/3 of the way down the center crease flap.
Fold up the point that has been covered in the previous steps so that it secures the flaps against the crease.
Fold the paper in half (along the vertical crease you created in Step 1) so that all the folds made in the previous steps are facing outwards. The small triangular fold is now along what will later be the bottom of the plane.
Fold both side flaps down to the bottom so that the wings are perfectly aligned with the bottom of the airplane.
Unfold the wings slightly so that they are perpendicular to the body of the airplane and form a flat surface next to each other.
Test your airplane. Start with a gentle toss to see how your plane glides through the air. Experiment with more aggressive throws to see how high and far your plane will go.