"Don't tell me no; I tell you no!" is a classic example of a frustrated mother reprimanding her toddler. Certainly, other parents and even teachers of young children experience and/or understand this sentiment as they pursue the slow process of teaching infants and toddlers self-control and self-regulation. This article illuminates how teachers can use their knowledge about infants' and toddlers' growth and development to better facilitate their evolving abilities toward self-control. Early experiences with the physical and social environment have a tremendous impact on a child's social, emotional, and cognitive development. In guiding young children, what is appropriate and effective differs from child to child. As is frequently noted, children do not come with a manual. As professionals, however, they do have several good indicators of how to understand and care for infants and toddlers in group care. They need to build their knowledge base and understanding of the developmental characteristics of infants and toddlers in order to help teachers and caregivers determine whether a child's behavior is appropriate or inappropriate. They also need to remind themselves of this knowledge as they move from theory to practice. (Contains 2 figures.)