Put on the pants and mark the desired length with pins or chalk
Remove the pants and turn them inside out
Fold the hem up to the marked length
Press the fold flat with an iron
Fold the raw edge inward to create a clean cuff
Pin the cuff in place evenly around the leg
Sew the cuff by hand or with a sewing machine
Repeat for the other pant leg
Press the finished cuffs flat again