If you are tall, you have the opposite problem and need to lengthen the pieces of a pattern.  Generally, 3"-4" taller than average would require adding about an inch to the waist length.  To do this, you will cut your torso pattern pieces apart at the lengthen/shorten lines and spread the pieces apart 1", keeping the parts of the grainlines aligned.  The same applies to sleeve length.  This is why it is so important to make a test muslin before cutting into your fashion fabric!