Instructions
Stop actively pedaling forward, allowing the unicycle to coast for a moment while your feet remain on the pedals. Don't try to stop the pedals from moving while coasting.
Lean forward slightly and reverse the direction of your pedaling. Don't make a full revolution with the pedals; you don't want to go backwards. Apply just enough backwards pressure on the pedals to stop your forward momentum.
Pedal your feet slightly back and forth, moving your upper body slightly in the opposite direction of your pedaling so that you can keep your balance while remaining stationary. You may also put one or both feet on the ground once the unicycle has stopped if you don't wish to idle on the cycle.