know

be in the know

Definition: have inside knowledge about a situation

Talk to Tim. He's in the know
Are you in the know about the current crisis

know better

Definition: have knowledge about how one should behave

You know better than to do that
I wish he had acted differently. He certainly knew better

know-how

Definition: understanding of how a task should be done

I'd call technical support and ask someone with the know-how.
Do you have the know-how to upgrade our servers

know the tricks of the trade

Definition: possess the skills and knowledge to be successful in a particular task

Let's ask Tom. He knows all the tricks of the trade.
I think we need to bring in a specialist who knows the tricks of the trade

know one's ABCs

Definition: to understand and be capable of doing the basics

I don't think he should do this. He doesn't even know his ABCs 

know someone or something like a book

Definition: completely understand someone or something

She knows Jerry like a book 

know someone by sight

Definition: be able to recognize someone

I know Peter by sight. I'll got to the airport 

know something from memory

Definition: have something memorized

She knows the piece from memory
Can you sing "New York, New York" from memory

know something inside out

Definition: have completely knowledge of something

Susan is the expert. She's knows this stuff inside out

know the ropes

Definition: know how to do something

We need to bring somebody in who knows the ropes. 

know the score

Definition: understand the facts about a situation

I know the score. Don't try to fool me