Grosgrain ribbon (pronounced "grow-grain") is polyester, so slightly melting the edge prevents fraying.
Unfold your ribbon.
Fold one ribbon end over and align the first two creases. Pivot the cut end 45 degrees, keeping the two creases' center points intersected.
Take up the rest of the ribbon and swing it over this first loop. Align the ribbon's center crease atop the first two layers in your hand, pivoting 45 degrees in the opposite direction from above.
Keep pinching at your overlap junction for a tidy bow-- it can feel a bit like shuffling a deck of high-friction cards.
Be sure to check out the video that goes with this guide, which shows you exactly how all these folds are made!
Fold the bow in half lengthwise, then turn down the folded sides (accordion fold) to make a pleat.