"to hit the nail on the head"
When someone completely understands you or gets something right.
e.g. a conversation might run:
Bob: "I've just broken up with my girlfriend"
Jim: "You must be feeling lonely"
Bob: "You've hit the nail on the head"
"to see eye to eye with somebody"
To agree with someone, to understand their point of view, to get on with someone. e.g. "The Mother-In-Law and the Daughter-In-Law did not see eye to eye about how to bring up the child" i.e. they disagreed about how to bring up the child.
"to kill two birds with one stone"
To get two things done with one action e.g. 'I took the cat to the vet - she had her yearly vaccinations done and her teeth cleaned' - this is killing 2 birds with 1 stone.
"to put your foot on something"
I don't know about putting your foot on something, but if you put your foot in something or 'put your foot in it' means that you have said or done something that you shouldn't have done and you will get in trouble.
"to have a bone to pick with somebody"
Means you need to speak to someone about their actions, because their actions have made you angry or upset.
"to feel something in your bone"
To have an instinct for something, to think something is going to happen, although you do not have any facts to prove your feeling is correct e.g. "Something's wrong, I can feel it in my bones"
"to the cat before the horse"
Don't know this one. Sorry!
"to put a finger in too many pies"
To have your finger in many pies means that you have many options open to you. I've not heard the expression with 'too' in it.
"to get your teeth into something"
To really get involved in something. e.g. Paul finally had a work project he could get his teeth into.
"to keep an open mind on something"
To not make a decision, to not be judgemental. e.g. "She kept an open mind about spiritual matters"
"to take the law into your own hands"
When the police won't help you to sort out a problem with criminals, ordinary people sometimes take action against them.
"to turn the tables on someone"
To play a trick on someone, especially someone who likes playing tricks themselves. To surprise someone.
"to pay back someone in his own coin"
"to put all your cards on the table"
To be totally honest.
"to be in a person's book"
"to give somebody a wide birth"
To give a person plenty of space, because they maybe emotional e.g. angry or upset.
"to get more than you bargined for"
To get more that you bargained for means you get more than you expected. It can be used in a positive (honest) way or a negative (sarcastic) way e.g.
'When the woman bought her new car, she discovered she got more than she had bargained for - there was a gold necklace on the passenger seat'
'When the woman bought her new car, she discovered she got more than she had bargained for when the exhaust pipe fell off'
"to make short work of something"
To do something quickly with little effort.
"to be out of step with someone"
Not sure how to explain this one. Can anyone else help?