Sometimes it’s hard to separate fact from fiction. So many writers put themselves in their character’s shoes. You may be a very likable person. But when your character is so close to your own personality, you never know how your character’s going to be perceived.
Since first-person POV characters are telling their stories, the first requirement for your short story or novel is that they’re actually willing to to tell their story. This may sound easy but if your character is extremely introverted, then a significant event will have to happen before they spill their life story. Otherwise, your story won’t be as believable.
That’s not to say your character has to talk to someone in order to reveal tidbits of information, write in a journal or use a tape recorder. But you’re allowing readers to enter this character’s mind. Readers have to trust the character and the character has to have a story to tell.
Another option when using first-person POV is to carry multiple narrators. One of the easiest ways to do this is by separating each character’s viewpoint into chapters.
Using the example of the wife and cheating husband, you could write a complete novel based on each character’s own personal story.
For instance, in one chapter the wife may describe a dinner scene as pleasant and just like any other day. But maybe the cheating hubby loathes the Mrs. His account of the exact same dinner scene could be dramatically different. Perhaps he thinks his wife is trying to poison him and he can’t get his mind off of his mistress.
Try this workshop exercise for more first-person POV help:
Write a scene from a formal dinner party, complete with guests. Use first-person from the mansion owner’s viewpoint. Consider it a somewhat snooty tone.
Now rewrite the same scene from a different character’s viewpoint. Perhaps one of the dinner guests is the owner’s daughter’s date. She brought this fellow because he’s not the same type of “stock” as they are and she’s rebelling.