Action planning is a foundational process that enables individuals to organize, anticipate, and coordinate goal-directed behavior. Gaining insight into how this process develops is crucial for understanding both typical development trajectories and the challenges faced in neurodevelopmental disorders and disabilities. This chapter explores the multidimensional architecture of planning, distinguishing between cognitive and motor domains and introducing the concept of praxis as the dynamic interplay of motivation, ideation, and execution. It delves into the neurophysiological underpinnings of action, highlighting the roles of premotor and parietal cortices and the mirror neuron system in both action execution and observation. The chapter examines motor planning difficulties observed in children with developmental coordination disorder (DCD) and cerebral palsy (CP), emphasizing internal modeling deficits and impaired anticipatory control. The chapter also explores the rehabilitative potential of Action Observation Treatment (AOT) and draws parallels between motor and speech planning, offering new insights into the diagnosis of speech motor disorders such as apraxia and dysarthria.