Filtering is when you describe a character’s thought processes and
experiences rather than allowing the reader to experience them.
A filtered scene might read:
Turning, she noticed a handsome vampire standing in the shadows.
It seemed to her the expression on his face was disdainful and cold.
An unfiltered version of the same scene would read:
She turned. A handsome vampire was standing in the shadows, the
expression on his face disdainful and cold.
In the first passage, the reader is watching the character as the
character watches the vampire. In the second, the reader is watching
the vampire with the character – this gives it more immediacy and
impact.
Words and phrases that often indicate a scene or passage is filtered
include:
She noticed...
He saw...
She felt...
He tasted...
She heard...
He
remembered...
She
looked...
It seemed to her…
Synonyms for those words are filters too. Glanced, watched, recalled… The list is endless. Be sure to watch out for synonym phrases too. "He thought back to" is the same as "He remembered." Strike out the filters and simply describe the action.
Remember: we should be in the POV character's head, seeing the world through their eyes. Not standing beside them, watching what they do.