The locations of all fifty scraps, including those the player has not found, is available to players with a Rockstar Social Club account; it can be viewed under the "Checklist" tab.
The letter scraps look like white glowing pieces of paper laying on the floor. When the player is nearby, the sound of a piece of paper flapping in the wind can be heard. This can be useful for finding the exact location. The game will automatically be saved after picking one up.