Simply do not select any dialogue options the entire game. You can interact with objects or people, but do not click on any of the speech bubbles that appear above your character. Otherwise, you can play through the game normally.
The only exception is the very last dialogue option during the Epilogue of the game. A photograph of the surviving friends will fill the screen and a voiceover will explain what happened to each character. At this point, you MUST select a dialogue option to end the game and roll credits.