A save is a way of keeping files and the player's progression through the game. It is essential to progressing through the game faster. There are ways that a save file can be corrupt, whether the console is turned off while saving, reckless modifications and through glitches.

Description

There are two types of save: manual and auto. Manual saving is a type of save where players need to save a file through campsite or safehouse. It can be made available when making a campsite, or sleeping in a bed in Safehouses.

Auto saving is where the game save files automatically, most often after missions are completed. Auto-save is also enabled when changing setting and can be disabled in the options menu.

Manual saves advance the in-game clock by six hours, similar to that in GTA games.  Setting up a campsite and simply choosing 'Save' will advance the time by 6 hours.  Saving a game isn't necessary to advance time (see next section).

Ways to Save

Manual saves

• Press Y (XBox) or Triangle (PS3) while in a Safehouse (beside the bed) or Campsite.  This will save the game and advance the game clock by six hours.
• If the player attempts to save at a safehouse or campsite, but then cancels the save, 6 hours will still elapse. Choosing a save file is not necessary. This can be repeated as often as the player likes.  
• Save Marston's location by placing a Campsite anywhere in an open flat area, away from roads, water, towns, and hideouts.

Game autosaves.  Autosaves do not advance the game clock. 

• Completing a Story Mission, a stage of a Stranger Mission, or successfully completing a Random Encounter,  Bounty Mission or Gang Hideout
• Completing a level of an ambient challenge or an outfit requirement
• Completing a job such as nightwatch or horse breaking.
• Succesfully evading law enforcement, posses or bounty hunters

Useful quicksaves (forced autosaves). 

• Using a horse deed from the satchel.  For best use of this feature, have at least two horse deeds in your inventory since Marston can't use the deed for his current horse unless said horse has been dead for about 5-10 seconds (whenever the "Skin Animal" prompt becomes present).
• Hitching a horse at a hitching post
• Taking a Wanted Poster
• Playing at least one hand/round of any gambling game and exiting

Glitches and Bugs

There are several known glitches when saving the game at a safehouse. The first is that the player has killed all the Buffalo and has the trophy "Manifest Destiny". The player saved the game at the safehouse and after doing this turned off their PS3. When the player turned it back on and loaded up the game, they still had the trophy but their stats said they had not killed all the Buffalo.