I like these quotes relating to Clarisse. I think she becomes Montag's first true friend: possibly the only one he's ever had, since she's the only person to really care about who he is. It's striking how small of a role she plays, yet her significance to Montag is indelible. On one of their walks, Clarisse admits to him:
You're not like the others. I've seen a few; I know. When I talk, you look at me. When I said something about the moon, you looked at the moon, last night. The others would never do that. The others would walk off and leave me talking. Or threaten me. No one has time any more for anyone else. You're one of the few who put up with me.
To me, that's a pretty good definition of friendship... someone who makes an effort to see what you see, to go against the grain to be there for another person. Later in the book, Montag tells Millie about his friendship with Clarisse, and how it helped him to see that he really disliked who he was, who he spent time with, and what he did:
And Clarisse. You never talked to her. I talked to her. And men like Beatty are afraid of her. I can't understand it. Why should they be so afraid of someone like her? But I kept putting her alongside the firemen in the house last night, and I suddenly realized I didn't like them at all, and I didn't like myself at all any more.
Clarisse helped Montag to become the person that he truly wanted to be. I think that speaks to friendship very well.
If I were you I would want to start looking either at the beginning at the strange friendship Montag strikes up with Clarisse, or at the end, when Montag finally escapes and joins Granger and his strange assortment of friends and companions, who have all memorised one text. By the end of the novel, Montag has a purpose and is part of a group that is united by that same purpose: the memory and preservation of literature for when it is needed. He has moved from being isolated and friendless to being part of a cohesive group united together. Note how he is described as being a part of the group and helping them in their task by remembering the Book of Ecclesiastes:
"Montag." Granger took Montag's shoulder firmly. "Walk carefully. Guard your health. If anything should happen to Harris, you are the Book of Ecclesiastes. See how important you've become in the last minute!"
Montag then is shown to have finally found a place and a community where he belongs, and the last few pages of this novel make the friendship that he has found evident.