Final answer:
FEMA is the agency responsible for coordinating disaster preparedness and ensuring a collaborative response from all involved agencies during a disaster.
Step-by-step explanation:
During the preparedness phase to ensure that all involved agencies work flawlessly during a disaster, the agency that should be contacted to provide guidance is the Federal Emergency Management Agency (FEMA). FEMA is charged with assisting state and local governments in times of natural disaster and is responsible for coordinating different agencies to utilize the rescue infrastructure effectively. Their expertise and resources are crucial for disaster preparedness and ensuring an effective response to emergencies.