When the reader is on a page written in Deep POV, they should be so deep inside the character’s head they become the character. They enter the room as the character; see only what the character sees, notices what they notice. Any sensory experience the character experiences would be the same for the reader. The reader will experience the same emotions the character is feeling.
Deep POV may be written in first or third person. Whatever you choose, you must be able to show the reaction of any other characters in the scene only through the eyes of the character in whose head you are writing. Here is a quick excerpt written in Deep POV:
John unlocked the door. He stood on the porch for a moment, steeling himself against the flood of memories threatening to swamp him. He gave the door a nudge and it swung open, the hinge still squeaking because she would never think to oil it. Maybe he should have stayed. Maybe if he had, Jen wouldn’t be dead.
He swallowed the taste of bile and stepped inside. The scent of gardenias, her favorite, filled his senses, choked him with recollection. His fingers shook as he reached for the switch and the crystal chandelier spangled the foyer with light. Too much. Too much. The room crushed him. Furniture and art work pressed in from all sides. Perhaps this was why his apartment was so sparsely furnished.
A pile of papers to the right of the door had spilled through the mail slot. He gathered them and sorted quickly before dropping everything on the credenza. The letter that fell on top caught his eye. He realized he had stopped breathing. It was written in Jen’s own handwriting.
In this short introduction, a man entered a house and picked up the mail by the door. This is all of the action that took place. But in Deep POV you are in his head and you see what he sees; feels what he feels. You notice that not once did I write, “he felt…”
Describing a character’s feelings externally can come off as distancing the reader. Showing the character’s feelings from the inside makes the character more important to the reader. This makes the character easier for the reader to know. You will also notice that I didn’t bore you with a description of the room, but you can see it through his eyes and the way he feels about it. We do not care that the Victorian sofa is covered in pink velvet. We do care that the room is overstuffed with furniture and artwork and that it stifles, crushes John. We want to know why. We don’t know if Jen is his former lover or spouse, his mother or sister or a co-worker, but we do know that she is important to John. He is experiencing strong feelings. Hopefully, it would make the reader want to turn the page.