It was recognized early in the development of the ICS that the critical factor of adequate planning for incident operations was often overlooked or not given enough emphasis. This resulted in poor use of resource, inappropriate strategies and tactics, safety problems, higher incident costs, and lower effectiveness. Planning involves evaluating the situation, developing incident objectives, selecting a strategy, and deciding which resources should be used to achieve the objectives in the safest, most efficient and cost-effective manner.
The primary phases of the planning process are essentially the same for the Incident Commander who develops the initial plan. For the Incident Commander and Operations Section Chief revising the initial plan for extended operations, and for the incident management team developing a formal IAP, each following a similar process. During the initial stages of incident management , planners must develop a simple plan that can be communicated through concise verbal briefings. Frequently, this plan must be developed very quickly and with incomplete situation information. As the incident management effort evolves over time, additional lead time, staff, information system, and technologies enable more detailed planning and cataloging of events and lesson learned.
In my opinion the planning process is the most helpful in the Subdivisions of the ICS chart. During any incident it is important to always have something planned before anything ever happens that way you are always prepared to react. You must give yourself time to analyze every situation and actually take action towards what you have planned. Without planning anything during the incident you will panic and not know what might happen along the way, even though in all cases things happen unexpectedly but if you have something planned you can go by that and hope it may go by smoothly. With all that said, between operations, planning, logistics, and finance/administrations from the Subdivisions of the ICS chart, planning is the most common function that should take place.