The emptiness of the society can be inferred from some of the conversations that Mildred has with her friends, and with some of the things that Beatty tells Montag during his little history lesson. Also, in Bradbury's descriptions of Mildred.
For the conversation between Mildred and her friends, look in the middle of section two of the book, "The Sieve and the Sand." They sit around talking about how they can't stand their children, how their husbands are never around, and how their t.v. shows are their lives. Montag says that their faces remind him of the faces of a bunch of statues that he ran across in a church once--cold, empty, stone faces that "meant nothing to him...there was nothing, nothing" at all behind their faces. Later he describes how they "sit there in the great hot emptiness." So, those are a couple quotes that indicate emptiness (pages 95 and 99 in my book; however, your version might not be the same). The title of the second section, "The Sieve and the Sand," indicates emptiness too because the more sand that you pour in a sand, it still remains empty. That is how people in their society are--empty, even though tons of stuff (entertainment, useless facts) are being poured into their heads.
Beatty's conversation comes towards the end of section one of the book. Beatty says that to make people feel happy and full, while they are really unhappy and empty, they
"cram them full of noncombustible data, chock them so damned full of facts they feel stuffed...they'll feel they're thinking, they'll get a sense of motion without moving."
So, the people are filled with useless information, but none of it is helpful...they are really just empty vessels walking around with nothing of importance in their heads. (page 61 in my book)
Another great place to look is Bradbury's descriptions of Mildred in the first few pages of the book. He describes her as motionless, emotionless, cold, still, and empty. He describes her sleeping "like a body displayed on the lid of a tomb," which indicates she is empty of life, vivacity and soul, just as everyone in their society is. He goes on to say, "the room was indeed empty," even though his wife was right there on the bed. Her presence made no mark--she was so empty it was like she wasn't there. (page 12 in my book)
I hope that these thoughts help to get you started. Good luck!