Social robots can act autonomously by interpreting and understanding social cues. Humanoid-typed social robots have a human-like appearance and can use voices, facial expressions, postures, and gestures as humans do. Therefore, it is possible to design the user experience by applying human communication methods to the social robot. Communication can occur as verbal and nonverbal communication. When starting a conversation, people use both verbal and nonverbal expressions. If we give sociality to the robots by applying human verbal and nonverbal communication methods to their design and operation, it will be possible to promote the natural interaction between the robots and the humans. In this study, we focused on the start of conversation as one of the stages of human interaction and explored whether we could apply existing conversation-starting strategies when a social robot participates in dialogue between two people. We investigated the user's perception based on those four strategies (asking a question, adding to conversation, looking alternately at others, and clearing one's throat). The robot's sociability, intelligence, politeness, and likeability was positively evaluated when the robot asked a question as a verbal engagement strategy, followed by adding to conversation, clearing one's throat, and looking alternately at others.