Keep the plants actively growing after blooming. Remove the spent blooms quickly to discourage seed formation.
Move the plants to a cool, but sunny, location and provide them with liquid fertilizer. Water regularly until foliage yellows, then taper water off over the course of about three weeks.
Allow the leaves to die back on their own. Remove the brown foliage before moving the bulbs to a prepared outdoor spot or pot. Allow the bulbs to go dormant.
Feed the bulbs in the spring with a liquid fertilizer or a granulated slow-release fertilizer and water regularly. Allow the foliage to green and die back without intervention so the plant can store plenty of food for the winter.