What are filter words? Basically, any word that separates the reader from the character. Here's a starter list:
Instead of using"see," just write what the character sees.
He saw the cat climb up the tapestry.
The cat climbed up the tapestry.
Removing filter words from my work has been both the toughest and most rewarding work I've done as a writer. The result is tighter, crisper prose. The trick is to begin thinking that way. I'm still figuring things out as I continue on my journey as a writer in pursuit of deep third person POVs.