Sprinkle the bread lightly with water
Wrap it in aluminum foil
Warm it in the oven at 300°F (150°C) for 5 to 10 minutes
Microwave it with a damp paper towel for 10 to 20 seconds
Steam it briefly over boiling water
Store it in a sealed bag with a slice of fresh bread
Use it in soups, bread pudding, croutons, or breadcrumbs if it is too hard to restore