Vacuum the sofa using the upholstery nozzle that came with your vacuum. Be sure to remove the cushions and vacuum them. Push down on sofa seat and push the vacuum's nozzle into the crevices at the bottom of the armrests and the back of the couch. Vacuum the back of the couch and the sides. Regular vacuuming will keep dirt and dust from getting ground into the fabric, making it easier to clean.
Spot clean the sofa using a cleaner that was designed for linen. Test the cleaner on an inconspicuous area of the couch to make sure it is color safe. Do this by spraying a bit of the cleaner in one spot and dabbing it with a piece of paper towel. None of the color should come off. Use the spot cleaner according to the product's directions.
Wash the cushions covers only when necessary. Linen cushions usually unzip from the couch and can be laundered. Some of them are preshrunk but many of them aren't. If you shrink your cushion covers they will not fit back on the couch. Read the label for washing instructions. When in doubt, wash the cushion covers inside out, in cold water with a mild detergent on gentle cycle. Hang them to dry.