Harvest fresh blooms for use as cut flowers or in bouquets after roughly ¼ of the lower flowers have begun to open. Cutting off the stalk too soon may cause the flowers to fail to open, and you'll lose the full benefit of the stalk.
Trim back the dying stalk of orchid plants halfway down after all of the flowers on the spike have opened and died back naturally. Leave the remaining half of green stalk in place to see if a new flower spike will emerge from it. If no new flower spike appears, the nutrients within the spike stub will redistribute down into the orchid plant roots.
Sever the last half of the flower spike once it has shriveled, turned brown and become desiccated. Cut the spike at its base between the leaves or just above the pseudo-bulb and discard it.