Be Proactive. Know the tendency of a colony about to swarm and prepare counteractive measures. A colony does not decide to swarm overnight. Certain measures lead to swarming. Be attentive of these proceedings:
Size of the Brood Nest. Honey bees instinctively decrease the size of the brood nest in preparation for swarming. Imagine a populated colony capable of caring for ten full frames of brood. After swarming, half the population will only be able to manage half the amount of brood. Room will be alleviated to store nectar and pollen as the colony begins to reduce the size of the brood nest. Beekeepers may mistake this as a honey bound hive when in fact the colony is prepping to swarm.