Or: Lock Yourself in a Meat Head.
The comments: "You're headhopping." Or "You switched POV's." Or "This part is confusing."
What they mean: You have just described something that your POV character cannot possibly know (unless you're writing scifi/fan in which your world has telepathy/some method of reading each other's minds, but if you're still getting the "headhopping" comment, you've not made the distinction clear enough).
If you're saying "Hold up, J. I'm totes writing in third person omni. That means I can jump into any head I want." Well… "Nah, seriously! That's how Tolkien did it. And C.S. Lewis. And Judith Krantz."
Calm down, Skippy. I get that a lot of books and stories employ third person omni and this post isn't about that. (Moar on omni later.*) For simplicity's sake, this post will address stories written in first person/third person limited POV. (Does first person omni exist? Yes. Yes it does.) The key word here is "Limited." That means, no matter how hard you try, you can't possibly know what I'm thinking right now. Go on. What do you think I'm thinking? Did you guess "Galactose"?
No, you didn't. Because you are stuck inside (limited by the meat and bone of) your head, and no matter of wishing, hoping, bargaining with debils, will ever let you see/hear/etc through mine.
Quick fix: Lock yourself into your POV character's meat head and do not describe anything the character cannot possibly see, touch, taste, hear, feel physically or feel emotionally.
Let's put our serious pants on.
Awfully generic example for us to deconstruct:
"Professor Grace was at her lab station with her back to the door. I crept in, sat down at my bench, and smiled like I'd been there for a while. When she saw me, she was afraid. I waved, happy that I'd finally gotten her attention with my blood-caked cloak. She was angry. Behind her desk, she assembled a shotgun. Then she raised it and aimed it at my face."
Why is it headhopping? Here is the key: The use of the word "I" should show you that this para is in first person POV. That means we are in one head (I is singular) – the narrator's head. I have put you inside ONE person, with ONE set of eyes that look only two ways: outside at the world, and inside at internal thoughts and emotions. ONE set of ears. ONE nose. ONE mouth. Let's deconstruct the para:
"Professor Grace was at her lab station with her back to the door. (This is the narrator, me. I see Grace through my one set of eyes. I am describing her location in relation to the room.) I crept in, sat down at my bench, and smiled like I'd been there for a while. (This is the narrator, me. I am describing what my own body is doing.) When she saw me, she was afraid. (BAM! Headhop! Why? How would I, the narrator, know what Grace feels? NOT headhop would describe what she looks like: here eyes widened.) I waved, (This is me, the narrator, doing something. Not headhop) happy that I'd finally gotten her attention with my blood-caked cloak. (This is me, narrator, feeling something. Of course I know I am happy because the feeling is inside me.) She was angry. (BAM! Headhop! Why? Because the only way I, the narrator, could possibly know how Grace feels is if I somehow left my body (hopped from my own head) slithered into Grace's body, and felt that anger while in Grace's body. NOT headhop would be: she glared. ) Behind her desk, she assembled a shotgun. (BAM! Headhop! Why? The key here is "behind her desk" which shows that the desk is between us. Again, unless I have left my body, I could not possibly know what Grace is doing behind her desk. Knitting a sweater? Fixing me a sandwich. I don't know.) Then she raised it and aimed it at my face."(NOT headhop would simply be: She got a shotgun from behind her desk (I can see this!) and aimed it at my face.)
Here's another awfully generic example:
"Sarielle approached Gozer the Great slowly. She'd heard stories of his awesomeness, and it made her both fearful and excited. Gozer uncoiled and lifted his head. He was angry at being disturbed, and wanted to kill Sarielle. She took a deep breath and found courage. Gozer admired this, and decided not to kill her."
See the headhopping? A little tricky with such a short segment, so let's deconstruct it:
"Sarielle approached Gozer the Great slowly. (Ok, two characters in one scene; it's unclear whose POV we're in. But ->) She'd heard stories of his awesomeness, and it made her both fearful and excited. (This sentence should firmly ground you in Sarielle's POV. Proof we're in Sarielle's head would be "she'd heard" – we are in her head, hearing; and "it made her both fearful and excited" – we're in her head, feeling these feelings.) Gozer uncoiled and lifted his head. (Still in her head. Sarielle is seeing this. Therefore, we are seeing this through one set of eyes: Sarielle's eyes.) He was angry (BAM! Headhop! How would we know what Gozer is feeling? We're in Sarielle's head. Unless we HOP out of Sarielle's head and into his, there's no possible way we could know what Gozer is feeling. Nothing in the paragraph has even hinted at this.) at being disturbed, and wanted to kill Sarielle. (BAM! Headhop! Again, unless we HOP out of Sarielle's head and into Gozer's, we would not know what he wants.) She took a deep breath and found courage. (Not headhopping. We are in Sarielle's head, so we should know what she does (she takes a deep breath) and what she feels (she finds courage). Gozer admired this, (Headhopping.) and decided not to kill her. (Moar headhopping. These feelings are in Gozer's head, not Sarielle's.)"
So stay in your POV character's meat head to avoid "headhopping."
* Omni requires a long discussion and including it here would have violated my "each post shall be less than 1000 words" rule. I pwomise we'll get to it!