All ears          To say that you are all ears means that you are listening very attentively. 
                        "Of course I want to know - I'm all ears!"

Bark up the wrong tree    A person who barks up the wrong tree is doing the wrong thing, 
                                              because their beliefs or ideas are incorrect or mistaken.

Bide your time    If you bide your time, you wait for a good opportunity to do something.

                               "He's not hesitating, he's just biding his time.  He's waiting for the price to drop."

Burn the candle at both ends    If you burn the candle at both ends, you exhaust yourself by doing too much, especially going to bed late and getting   up early.

                                                         "Scott looks exhausted - I'll bet he's been burning the candle at both ends lately."

Couch potato        If you refer to someone as a couch potato, you criticize them for spending a lot of time sitting and watching television.

                        "Don't be such a couch potato.  There are better ways of spending your time than in front of the TV."

Disappear into thin air   If someone or something disappears into thin air, they vanish in a mysterious way.
                                            " After being accused of embezzlement, the director disappered into thin air."

False move     In a dangerous or risky situation, if you make a false move, you do something which may have unpleasant  consequences.

 Go with the flow    If you go with the flow, you follow the general tendency and go along with whatever happens.

                                   "When my colleagues organize an office party, I just go with the  flow when it comes to the details. "

Your wish is my command!   This is a humoristic way of saying that you are willing to do whatever the other person asks.
                                                     "Breakfast in bed? Your wish is my command!" 

Sell your soul    This is a humorous way of saying that you would be willing to do something morally or legally wrong to obtain what you want.

                              "He'd sell his soul to get an interview."