filtering - fave pet peeve:
What a publisher has to say ( not me ) With grateful thanks to my editor:
Filter words are words such as:
felt, thought, decided, wondered, remembered, knew, realized, figured, assumed, worked out, saw, looked, and heard.
These are all words which 'tell' the reader information rather than 'showing' it (ie. giving them the impression that they're discovering it for themselves). Of course, all writing is actually telling, but these words make the process a little more obvious.
It is often fine to use filter words—they can be an effective and economical way of conveying information to the reader. However, if they're used too much, and particularly if they're used in action scenes, they can distance the reader and slow the pace. This is because the reader gets the information through the 'filter' of the character's experience, thus reminding them that they're being told about the scene.
For instance, these are two passages that convey the same information (filter words in bold):
I walked down the hill through the long damp grass. I decided to climb the fence. I felt nervous, wondering if the guards were nearby.
The grass brushed dew against my legs as I walked down the hill. Above me, the fence glinted silver in the moonlight. Keeping alert for the sound of the guards, I sought out handholds to climb it.
Of course, there is no need to get rid of all filter words. But do you see how the reader still experiences what the character is experiencing, without needing to be told what the character is wondering/thinking/seeing?
Generally, this technique is preferred to using a lot of filter words, because it gives an impression of being more deeply in the character's point of view, and because it can have a more colorful and immediate effect, thus bringing the reader into the story better.