The Store, Buy, Sell, Assemblies and Make modules must be implemented before the Plan module can be used. Your stock levels should be accurate and your assemblies should accurately reflect your product structures. The lead times and ordering parameters held for each of your partnumers should be realistic.
Initially it is wise to restrict running a plan explosion to a selection of your products until you have gained experience in its use. Enter sales forecasts for the test products (using the forecasts tool) and then run the plan explosion on the forecast figures.
Print out the plan action reports and compare the suggested actions with what you would normally expect to order.
When you are confident that the Plan module is giving you the results you expect, enlarge the plan and run the plan explosion for a wider range of your products.