Introduction: The main aim of this series of three articles is to explore the question of what it is that makes ‘good’ language learners, what individual factors can influence the learner’s success in foreign language learning, and what teachers and learners can learn from those who succeed in this complex task. In Part I., the author reviews a number of research studies on the ‘Good Language Learner’ issue; she also attempts to summarize the main characteristics, strategies, and behaviours of successful and unsuccessful learners. Part II. presents an overview of studies focused on the role of selected individual differences and shows how the variables may influence the process and outcomes of language learning; it also indicates which strategies and behaviours of ‘good’ learners can be taught and learnt in the classroom. In Part III., the author explores the issue further and presents the results of her empirical studies aimed at identifying the features and strategies of both successful students of English as a foreign language and learners with lower achievements. Material and Methods: A number of formal structured pen-and-paper questionnaires, oral surveys and learner diaries were employed to diagnose the participants’ personality traits, learning preferences and patterns of strategy use. Results: The results of the research indicate that ‘good’ and less efficient learners tend to use strategies differently. Conclusions: The pedagogical implications for L2 teaching and learning discussed in the series are closely related to the ideas of strategies-based and styles-and-strategies-based instruction in language education, self-regulated or autonomous language learning, and continued lifelong learning.