The document outlines three principles of instructed second language learning aimed at creating optimal learning conditions for students. It emphasizes the need for teachers to make their intuitive teaching theories explicit and to evaluate their methodologies against these principles, illustrated through case studies such as Juanita Watts' evaluation of an information-gap task in her classroom. The principles advocate for a balance between developing formulaic expressions and rule-based competence, ensuring a focus on meaning during instruction, and the necessity of attention to form to facilitate language acquisition.