Final answer:
Effective planning of variable overhead costs aims to perform activities that add value for the customer, align costs with production levels, and manage diminishing marginal returns.
Step-by-step explanation:
In the context of managing a company's overhead costs, effective planning of variable overhead costs means ensuring these costs only arise from activities that add value for the customer who uses the products or services. Unlike fixed costs, variable costs such as labor and raw materials change with the level of output. These costs should be managed in a way that aligns closely with variations in production volume while also adding value to the end consumer.
Considering variable costs show diminishing marginal returns and the marginal cost of producing higher levels of output rises, it is crucial to plan for these costs judiciously to ensure efficient production without unnecessary expense.