The best way to sharpen scissors is by using a sharpening stone. Holding the scissors on your hand, open them and slide the sharpening stone on the blade. Continue sliding until the stone until the scissors are sharpened as desired. Find out more details at http://www.ehow.com/how_6521647_way-sharpen-scissors.html.
If you want to do it yourself you can buy scissor sharpeners. My Mom and aunt had them for their scissors they used for sewing. You can find them anywhere that sells fabric and sewing things. Most walmarts have them.