Clean up spills as quickly as possible using a warm, wet rag. Avoid wiping the drywall off the floor, rather use the rag to try to pick up any drywall chunks. Dab at the drywall stain as opposed to smearing it.
Apply an adhesive remover or anti-mastic to the affected area of the floor if the drywall dried before you were able to clean it. Wear gloves while pouring either product to avoid getting it on the skin. Allow the product to remain on the affected area for 30 minutes.
Scrape at the drywall with a plastic putty knife as it should have softened by this time. Dispose of the compound in a trash can and scrub any remaining residue forcefully with a clean rag.