Tenses
The most distracting mistake an author can make is probably a tense mistake. If you write "Bob crossed the room and bought a bagel" in one sentence and then you write "Marsha gazes at Bob lovingly because she thinks he is handsome," the reader can easily get confused (or at least annoyed).
My opinion is that authors should use only one tense (past or present) in narrative/description until they understand the possible exceptions. Most of the time, it will be grammatically correct if you just stick with one tense. However, if you try to experiment and mess it up, it will be painfully obvious.
Some Tense exceptions:
1. The 1-2 sentences at the beginning and end of flashbacks (but usually not the sentences in the middle of flashbacks)
If you normally write in present tense, the exception sentences will be in past tense. If you normally write in past tense, these exception sentences will be in present perfect tense. Example of present perfect tense:
I had eaten a pie yesterday, but I had not enjoyed it.2. If something is still true in the present
If you normally write in past tense, but you say something that is still true for the character/place "today," you can write that statement in present tense.
I walked across the room and looked in the mirror. I have brown hair, and my eyes are blue.Note: In stories that are written in past tense, you're operating under the assumption that the character lives through whatever trials that happen in the story, and then they look back on the trials to tell their story in past tense. No one usually mentions this in the story, but it's technically true. That's why there's a "today," as opposed to the "yesterday" during which the story actually happens.
Point of View (POV)
I say there are four types of POV, but only two of them are really valid in this day and age. Of course, that's just my opinion, but I've got some reasons for that opinion. One way or another, most writing books I've read agree that unless you're a bestselling author already, you shouldn't experiment with using the two uncommon types of POV or with combining different types of POV in the same book.
However, you can have the same type of POV with different POV characters in the same book (more guidelines on that below). I'll start by describing the types of POV.
Types of POV
1st person - You've all seen this one if you're a fan of romance. It's a staple in stories where you want the reader to be very close emotionally to your POV character. Your reader knows absolutely everything about your POV character's thoughts/history (unless you have an unreliable narrator, which is when the POV character has amnesia, is insane, is lying, or has some other mental problem that makes them unable to accurately convey what's happening in the story).
There are generally only one or two POV characters in a 1st person book. You can technically italicize thoughts in 1st person, but it feels unnatural because the reader is supposed to be completely in the POV character's head.
I sing all the time because I love listening to my own voice.2nd person - Please don't use this unless you're doing one of those "choose your own adventure" books. This is where the reader is the POV character, and it's really strange to see it in a normal novel. I don't know much about it because hardly anyone uses it outside of "choose your own adventure" books.
You love cake. It's your favorite thing in the whole world. You bought some at the store today.3rd person limited - This POV is emotionally farther away from the POV character than 1st person, but it's emotionally closer than 3rd person omniscient. Think Harry Potter. The reader knows what the main character is feeling/thinking, and the events of the story are colored by the POV character's thoughts/history.
However, there's a little distance between the reader and the POV character. If stories in this POV have multiple POV characters, they usually have between 2-5, though it is technically possible to have more than 5 POV characters.
In this POV, thoughts can be stated in the text, or they can be italicized. If the thoughts are italicized, they should usually be in present tense. If they're not italicized, they should usually be in past tense.
Non-italicized example:
Marie went to the mall. She looked through her favorite clothes store and smiled. This was the life.Italicized Example:
Marie went to the mall. She looked through her favorite clothes store and smiled. This is the life, she thought. I could do this all day.3rd person omniscient - Though it's sometimes used in more plot-based stories like speculative fiction or science fiction, it's considered pretty old fashioned in most genres. Especially if you want to write for a younger audience (YA or middle grade), I would advise not using this POV. This POV is when you basically know everyone's thoughts and everything that happens.
In one paragraph, you're in the maid's head; in another paragraph, you're in the butler's head; and in the next paragraph, you don't even know whose head you're in because it's an Agatha Christie novel and she wants to keep you in suspense.
Mary loved Bob. Bob loved Mary, but Bob loved cats more. Mary hated that Bob loved cats. She killed his cats when he wasn't looking.There's another type of omniscient where you don't know anyone's thoughts, but you do know everything that's happening. I personally think reading that type of story is just boring (unless it's an old fairy tale).
How and When to Change POV Characters
Preferably, you shouldn't change POV characters more than once a chapter. If you have to change a POV character in the middle of a chapter, make sure that you insert a scene break before you change POV characters.
If you are writing in 3rd person (either kind), just make sure to say the POV character's name (usually NOT their full name, just their first name) in the first sentence of every scene they're in. If you're writing in 1st person, you want to say I/me/my in the first sentence of every scene they're in (this is especially true if you ignore my above advice and decide to have 3rd person in one scene and 1st person in another).
When you change from one 1st person POV character to another, I recommend putting the name of the POV character in the beginning of the chapter (either in the chapter title or written beneath it). You don't have to put their name again if there is a scene break or chapter break unless you change to a different POV character at that point.
Note: The name of the character should typically be left-aligned like the rest of the text and in bold text. Yes, I know I said you should never bold words in novels in another article, but this is the one exception I can think of.
How Many POV Characters
Only use as many POV characters as you need. Extra POV characters start to get boring/confusing. I gave some suggestions about numbers above, but I would say that overall, you should stick to one, maybe two, POV characters per book unless you're doing an epic fantasy with a dozen main characters.
One thing you have to keep in mind: all POV characters should be fully developed characters with a history, a unique personality, and an interesting view of life. They should be someone you want to root for (even if they're a villain).