List some of Montag's conversational mannerisms.

During Montag's first interaction with Clarisse, the reader gets a sense of his mannerisms. Montag attempts to portray himself as an amiable person who does not take his job too seriously. Montag is used to having superficial conversations, which usually amount to dismissive small talk. However, Clarisse is an extremely introspective, curious person who begins to make Montag feel awkward and anxious. Montag does not seem comfortable when Clarisse pauses during their conversation, and he prefers to continue elaborating on senseless topics to keep their conversation moving.
When Clarisse mentions that she heard firemen used to put out fires in the past, Montag reveals his typical mannerism of abruptly laughing. Clarisse responds by questioning Montag about why he instinctively laughed when she did not say anything funny. As their conversation continues, Montag instinctively breaks out into laughter several more times because he is uncomfortable. Bradbury also mentions that Montag "clenches" when there are silent gaps in their conversation.
Overall, Montag's mannerisms indicate that he is an anxious individual who is not used to having enlightening conversations and feels more comfortable engaging in small talk. His mannerisms include abruptly laughing, attempting to keep the conversation moving, clenching, and engaging in rather fragmented speech without deeply elaborating on specific topics of conversation.