As a writing mentor, beta reader to the masses, and editor, I often see a word that gets my attention for being overused, and as I've learned from my own personal experience, many writers have no idea that an innocent, insignificant word insinuates it's way into stories--again, and again, and again, to the point where readers might count the occurrences.
Many words are guilty, but the one I'll focus on today is "turn."
He turned. She turned. Turning his head... etc.
What's wrong with "turn"? you ask.
Lots. Mainly because, in most cases, it imparts no crucial information and is unneeded.
For example, many times I've read a scene in which two characters are talking, facing each other, then one "turns" to the other. Or, the author is unclear as to the characters' positions, so "turn" isn't needed because we had no idea they weren't already facing.
And worst case scenario, the characters "turn" in one sentence and "turns back" in the next. (Unless they're a werewolf, one or both is probably not needed.)
So be careful when writing, and if you absolutely must use "turn" in the book, be sure to look up synonyms or find other word choices to avoid repetition.