Put on the shoes you will wear with the pants
Turn the pants inside out
Try on the pants and mark the desired hem length with pins or chalk
Measure and mark both legs evenly
Remove the pants
Fold the fabric up to the marked length
Press the fold with an iron
Pin the fold in place
Cut off excess fabric if needed, leaving enough for a hem allowance
Fold the raw edge under to create a clean hem
Pin the hem securely
Sew the hem by hand or with a sewing machine
Remove the pins
Press the finished hem flat
Repeat for the other leg if necessary