Utilizing the methodology of Conversation Analysis (CA), this study examines teaching moments observed in free conversations by pairs of Japanese and American friends. CA's detailed turn-by-turn analysis reveals that teaching of vocabulary, idioms, and culture occurs when native speakers orient to the non-nativeness of the other speakers. Native speakers of English recurrently produce "in America" and activate the other speakers' non-native membership categorization, which occurs abruptly in a sequence with a restart. There is no clear evidence why native speakers orient to it at a particular moment of the development of the sequence since prior sequences do not indicate that non-native speakers do not understand the introduced vocabulary, idioms or culture. In spite of the overt activation of the non-native membership categorization, native speakers construct the turns in a manner that they align themselves with non-native speakers by choosing the expressions such as "they say," "they call" or "it's called" instead of "we say" or "we call" in referring to what Americans say. This turn design of the use of the pronoun "they" and the passive construction may be due to the informal settings of the meetings; i.e., native speakers may be refraining from teaching plainly by taking a presumed role of an American, a native speaker, or a teacher in official teaching contexts such as classrooms or tutorials, but rather acting as in-group friends who share the same category. Secondly, data analysis from an emic perspective shows that teaching is trigged when responding to "oh/ah really" produced by non-native speakers; native speakers further inform or give accounts for personal stances which express their evaluations, opinions, perspectives, and assessments, including their understanding of other people's points of view. In subsequent sequences after "oh/ah really," by bringing up the geographical location "America" and using collective pronouns such as "they" or "everyone," native speakers generalize the actions as a routine habit among Americans where rich cultural information is shared. In addition, native speakers explain a public system or provide definitions of words. These turn components make the turns specifically designed for non-native speakers and demonstrate native speakers' orientation to the non-nativeness of the other speakers. Lastly, teaching moments of Japanese grammar are examined. A native speaker of Japanese deploys joint utterance construction (Hayashi, 2003a) by which post-positional items are latched to another speaker's on-going utterances to direct the subsequent interaction. The native speaker utilizes joint utterance construction possibly in order to make further corrections in the non-native speaker's statements. However, the non-native speaker does not yield turns and repeats grammar mistakes. The data show the non-native speaker's potential cultural misunderstanding due to a lack of understanding in pragmatic connotations of its practice. This study contributes to the fields of Second Language Acquisition (SLA) by analyzing the social interactional practices in free conversations by pairs of a native and non-native speaker and documenting the moment-by-moment development of teaching moments observed. It also supports the application of CA in SLA studies and highlights the importance of incorporating CA-based materials in language classrooms to promote interactional competence among language learners. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]