In this paper, we introduce a conversation support agent called Zinger. Zinger acquires the current interest of a participant, identifies a partner who has a similar interest, and recommends several topics related to the interest. This recommendation is expected to help the participant establish common ground in conversing with the partner. The participant can get valuable information with a successful conversation. Experimental results show that Zinger could promote utterances of 35% subjects. In addition, factors affecting the participant's utterances are examined by multiple regression analysis. The results suggest that providing helpful information and appropriate presentations can contribute to better utterances.