To clean a fabric lamp shade, a simple mild detergent works well. Laundry detergents, dish soaps and even hand soaps are gentle enough that they do not damage the fabric, yet still are strong enough to clean dirty lampshades.
The first thing to do is remove the trim from the lampshade. This eliminates the chance of any dye running down from the trim and staining the lampshade. Once the trim is removed, the lampshade should be completely submerged in a bath of warm water containing a mild detergent. Gentle detergents designed for silk and wool are the best for delicate lampshades. After moving the lampshade around in a circular motion in the water, the lampshade can be rinsed and set out to dry. If the lampshade still appears dirty, it may require a second bath.
To dry the lampshade, it is important to place it in an area where air circulates well. This helps keep the metal frame from rusting through the fabric as the lampshade dries. After the lampshade has thoroughly dried, the trim can be replaced with new trim or simply tacked back on with a few stitches or fabric glue.
If washing the lampshade is not an option, a piece of bread can help remove loose dirt and dust. Remove the crust from a piece of bread, standard white bread works, and roll the bread into a ball. The ball of bread acts as a lint remover. Roll the ball of bread across the lampshade by hand to pick up stray debris.