This dissertation explores the communication goals and social actions Korean speakers accomplish by using the sentence-ending (SE) suffixes -- ney, --ci, and --kwuna in conversation and suggests their pedagogical implications. This study also examines regularities in the sequential patterns (initiating, responding, and closing) and epistemic positions (subordinate, equal, and dominant) of the SE suffixes. In particular, the ney and ci-marked assessments and the kwuna-marked response tokens kuleh-kwuna/kulay-ss-kwuna are analyzed. This study integrates three methodologies of the Conversation Analytic (CA) approach, prosody analysis, and the corpus methodology. Data used in this study include naturally occurring spontaneous telephone and face-to-face conversations. The results indicate that the social actions conveyed by the SE suffixes are intertwined with their epistemic positions and sequential patterns. The ney-marked assessments are frequently used as an initiating action that solicits a response. It is also frequently used to serve the ideal roles of a listener as it may express empathy, praise, or encouragement to interlocutors and a subordinate epistemic position. The ci-marked assessments, especially in response, predominantly express agreement and/or confirmation from a dominant epistemic position. The response tokens kuleh-kwuna/kulay-ss-kwuna generally indicate a speaker's understanding and acknowledgment of the information received from his/her interlocutors. These response tokens, expressing epistemic balance and no evaluation regarding the information, often close a sequence of question and answer or topic, and provide a suitable environment in which speakers can move forward to the next turns. Prosody analysis of kuleh-kwuna/kulay-ss-kwuna shows that certain boundary tones and different levels of intensity accompany the productions of these response tokens and mark the actions of topic continuation or topic closing. This study clarifies the roles of epistemic positions, sequential patterns, and prosody (intonation and intensity) of grammatical resources in discourse. It also provides suggestions and specific activities for Korean language educators to teach the discourse functions of the SE suffixes and response tokens.