Summarize:

Remove excess food and waste and spot-clean the cage as needed with a wet paper towel. Scoop out any soiled bedding and replace it with dry, fresh bedding. This should be done every single day. If your guinea pig spills water into the food dish, remove that food and replenish the dish with fresh, dry food. Doing this every day will help prevent bacteria from growing in the food and water receptacles.
Spot-clean the cage. Refill food and water. Wash food and water dishes in hot, soapy water.