He knew that she knew that they knew that everyone knew characters who know too much suck

Amy knew she was late. (Bad)
Never use know unless it can't be avoided. In most cases you can just delete it.

Amy was late. (Better)
Most often after it's deleted the only verb in the sentence is "was."  When your characters know you are telling not showing. Telling can be useful. His hair was black. But for the most part, the transition achieved with was, can also be achieved with an active sentence.

Amy raced up the stairs and burst into the office twenty minutes late. (Best)
Know in every form is a weak verb. It doesn't have the same action that "raced" and "burst" have. 

Bobby Johnson knew the bully was about to hit him so he ducked. 
Even when used in conjunction with a stronger verb such as "ducked" knew is the primary action. It saps the excitement out of a scene. While it should almost never be used, it NEVER belongs in an action sequence. The only way to deal with it in an action sequence is to reorder the ideas. Start with who did the action first. The bully's fist flew at Bobby Johnson. He ducked....

Mike Roberson knew he was going to win the lottery...
Knew is the past tense form of know. But even though it is past tense it makes a prediction which may or may not be true. Thus there is really only one situation in which it really does belong. When your character can predict the future.

Mike Roberson knew he was going to win the lottery a year before he bought the ticket.
But I'm still telling you about Mike, not showing. This is a good example of when you can tell and not show.

This diatribe on "know" was sponsored by Book X.  Book X started off fantastic hoowever by chapter ten hardly a paragraph when by without a character knowing something. Sometimes they knew things two and three times a sentence.

I love books. I rarely complain about anything I read and I almost never put a book down. I'm not saying I'm immune to imperfections. Every writer does things I'd rather they didn't but as long as I'm entertained it doesn't matter to me.

However, the characters knew so much that I ceased to be entertained. Reading the story became painful as early as chapter four. I gave up at chapter ten. I just couldn't take one more "know." So please, your character should know anything, but if they must know something, then make sure they don't know much.

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