The article illustrates a foreign language teaching method based on the explanatory focus of the contrastive analysis (comparative analysis between mother tongue and target language) insofar as the linguistic knowledge of the student is taken into account in order to treat concrete cases and real phenomena of interaction between both languages. It deals with concepts such as linguistic interference and error, which serve as teaching and learning assessment parameters. Likewise, the article studies the teacher‟s competence, his/her action, his/her teaching style, his/her role, and his/her way to interact with the group of students. Some observation registration samples that have been carried out throughout the execution of an experimental course of English are included in the text (not participatory observation).