Calculate the amount of ribbon you will need by wrapping it around your box and making three loops: 2 loops approximately the size of your bow's loops, and one loop for the length of the bow's tail.
Give yourself a few inches of extra wiggle room and cut.
Find the center of your ribbon and place it on the center of the top of your box.
Flip your box over and bring the ends around each other and pull tightly to make a cross.
Like this. Pull your ribbon up and flip your box over again, top side up.
Slip the loose ends under the horizontal ribbon.
Check that everything is flat (no twists in your ribbon) And tie a single knot on top of the horizontal ribbon.
Make two loops. Both loops should have the open end on the your left.
Hold both loops flat and away from each other.
Keeping it nice and flat, fold the left loop (Loop 1) over the right loop (Loop 2).
Push Loop 1 under and through the opening. Don't bunch up your ribbons, keep it all as flat as possible.
This is the same picture as above with helpful illustrations!
Pull on the loop ends to tighten, but don't pull too hard! Keep the center knot somewhat loose and squarish.
Hold the center knot and pull on the tails and loops to adjust your bow to the size you want it to be. Tighten the knot slightly so it holds firmly, but isn't small and ugly. If you pull it too tight, get in there and loosen it up. Don't be afraid to be rough with the ribbon and squish the loops and knot around until it looks perfect.
Fold one tail in half and snip it at an angle to make a fishtail shape (upside down "V"). Repeat on other tail.
And you're all finished! A perfectly wrapped present! Yay!
See the rest if this tutorial:
Perfect Gift Wrapping Tutorial, Part 1: Preparing Your Package
Perfect Gift Wrapping Tutorial, Part 2: Wrapping Your Gift