How can I clean really bad stains from a cloth sofa?

Depending on the stain I've used Shout Laundry Stain remover. In theory if it gets stains out of clothing it should do the same for cloth couches. The spray has enzymes in it that break down certain stains. Spray the area and let it sit for a while. I usually follow the instructions on the bottle. Then with a damp sponge or cloth, start washing the stain away. Keep a bucket of water next to you, using the temperature it states on the bottle for the temperature of the water. Once it's removed you can air dry, blow dry it on a cool setting, or spot dry with a towel.