Men's dress pants should be hemmed so they "break," or crease very slightly, just above the top of the shoe, covering the shoe tops. The back of the hemline should come down to the sole of the shoe.
Pants that are too long can be shortened easily by a tailor, as long as they are uncuffed. Cuffed trousers cannot be shortened without altering the fit of the pants. Some shorter men prefer to hem their trousers slightly shorter than usual to create an appearance of increased height. Dress pants often come unhemmed to allow the new owner to have them tailored to his specifications.