How to hem a pair of trousers
A. Undo the existing hem carefully using scissors to cut the thread (not the trousers)
B. Get the trousers owner to try them on and fold each leg inward to the required length. Hold it in place with pins
C. Take off the trousers and turn them inside out. Measure the length of the fabric folded inward. Take out the pins and use this measurement to refold the pant legs all the way around evenly. Pin it back in place.
E. Iron the edge of the hem on both legs making a good crease.
F. Sew a straight seam through both layers of fabric around the edges of the legs about a quarter inch from the bottom fold. Fold the messy end of the fabric up one more time to hide the cut edge and iron the folds flat.