You might use at least one or more assistive interfaces which provide haptic feedback or visual feedback such as force, vibration, zoom-in and -out, rotating screen, etc. Have you ever thought about the importance of providing proper assistance? Excessive assistance for a skilled human user may slowdown task completion whereas insufficient assistance for a novice user may result in a task failure. This book introduces an approach to set a customized assistance policy for various users whose skill levels and task-performing strategies are different by adopting the strategy of an expert assigned to a user individually.