Book excerpt: This book is the compilation of eight research studies conducted by students from the Master's in Education with Emphasis on English Didactics at the School of Education in Universidad Externado de Colombia, and one study carried out by the professors from the same Emphasis. The articles focus on the role of teachers as materials developers in their English as a Foreign Language (EFL) context and the importance of developing contextualized materials to promote students' learning processes. These issues comprise several themes such as teacher-developed materials in a Master's programme in Education with Emphasis on English Didactics, helping high-intermediate students develop argumentative skills in writing, enhancing undergraduates' reading comprehension through the awareness of reading strategies, digital storytelling to foster EFL writing, the effect of combining two corrective feedback strategies on written errors correction, self and peer assessment on students' oral performance (CALLA), communicative games to foster oral interaction in the EFL classroom, and promoting the reading process through collaborative strategic reading (CSR). This book is divided into eight chapters. Each chapter explains the corresponding research process undergone by the students. It describes their theoretical considerations, instructional and research designs, data analysis and findings, and conclusions in relation to their concern.