The scenes in the "past" when Dean and Cindy are falling in love were shot first, in three weeks. After this, Ryan Gosling and Michelle Williams spent a month together in a rented house to age themselves in preparation for the "present" scenes. They spent a lot of their time grocery shopping, cooking dinner and learning to pick fights with each other.
When filming the argument scenes, director Derek Cianfrance gave instructions to Michelle Williams and Ryan Gosling individually, without the knowledge of the other, in order to create more tension between Dean and Cindy. For Williams, Cianfrance would instruct her to try to leave the room, use any way to break out of the argument with Gosling, etc. For Gosling, Cianfrance would tell him to use any means to persuade, get Williams's attention, etc. Gosling stated it was a new and interesting process, as it became a tug-of-war game on set.
Michelle Williams, Ryan Gosling, and Faith Wladyka actually lived together in a house in Carbondale, Pennsylvania for thirty days while the film was being shot. They struggled with the real stresses of having to share a bathroom and do the dishes three times a day. Their grocery budget was based on Dean's salary as a house painter and Cindy's as a nurse: $200 every two weeks. Gosling stated that it was hard for him and Williams to take off their wedding bands when it was over.
The film was originally set to shoot in spring of 2008, but it was delayed due to Heath Ledger's death. The producers and director delayed the film out of respect for Michelle Williams, Ledger's ex-girlfriend and mother of his daughter Matilda, rather than going ahead and shooting the film with another actress in Williams' role.
The tattoo on Dean's upper left arm is from the book "The Giving Tree" by Shel Silverstein. The book is about giving and sacrificing everything for another.