1) Open Pandora's Box-to uncover a lot of unsuspected problems-
Sadly, his reforms opened up a Pandora's box of domestic problems.
2) Spill The Beans-reveal secret information unintentionally or indiscreetly-
So who spilled the beans about her affair with David?
3) Hit The Nail On The Head-to describe exactly what is causing a situation or problem, to do something exactly right-
I think Mike hit the nail on the head when he said that this company lacks a feeling of confidence.
4) The Final Straw-the last in a series of unpleasant events that finally makes you feel that you cannot continue to accept a bad situation-
Losing my job was bad enough, but being evicted was the final straw.
5) Pound The Pavement-to walk through the streets looking for a job-
Mary had children to feed, so she kept pounding the pavement until she finally landed a job at a burger restaurant.
6) Crocodile Tears-tears or expressions of sorrow that are insincere-
They weep crocodile tears for the poor and disadvantaged, but are basically happy with things as they are.
7) Achilles Heel-a small problem or weakness in a person or system that can result in failure-
Maths has always been my Achilles heel.
8) Method In Madness-a purpose or plan behind something that is seemingly crazy-
The way the houses were built seemed strange, but when we heard of the natural calamities affecting the region, we realized there was method to the madness.
9) Devil's Advocate-someone who pretends, in an argument or discussion, to be against an idea or plan that a lot of people support, in order to make people discuss and consider it in more detail-
The schoolmaster often played devil's advocate with his students so that they could have an interesting discussion and look at other point of views.
10) Jump On The Bandwagon-to join a popular trend or activity-
The success of the product led many firms to try and jump on the bandwagon.
11) To Each His Own-other people are free to like different things or have different preferences-
I don't care for football, but to each his own.
12) Best Of Both Worlds-a situation in which you can enjoy the advantages of two very different things at the same time-
She works in the city and lives in the country, so she gets the best of both worlds.
13) Go Back To The Drawing Board-to start planning something again because the first plan failed-
Our proposal might not be accepted, in which case we'll have to go back to the drawing board.
14) Actions Speak Louder Than Words-someone's intentions can be judged better by what they do than by what they say-
Of course the government have made all sorts of promises but as we all know, actions speak louder than words.
15) An Ace In The Hole-an advantage you have that other people do not know much about-
The local team has an ace in the hole with their new player.
16) Beat A Dead Horse-to waste effort on something when there is no chance of succeeding-
He keeps trying to get his story published but I think he's beating a dead horse.
17) Piece Of Cake-something that is very easy to do-
The exam was a piece of cake.
18) Take The Bitter With The Sweet-to accept both the good and the bad that happens-
If you intend to get married, you must be prepared to take the bitter with the sweet.
19) Be In Hot Water-to be in difficult situation in which you are in danger of being criticized or punished-
He found himself in hot water over his comments about immigration.
20) Bite The Dust-to fall, to die, to end in failure-
His career bit the dust when he lost his job.