1) Tip The Scales-cause a particular situation to happen or a particular decision to be made, when other situations or decisions are possible-
The teams were evenly matched until two quick goals from Rooney tipped the scales in favour of England.
2) Shooting Fish In A Barrel-something that is too easy-
Jane's a good mechanic. Changing a tire is like shooting fish in a barrel for her.
3) Go Against The Tide-to not follow what everyone else is doing-
It's very difficult to go against the tide and follow your dreams.
4) Sit On The Fence-to delay/avoid making a decision-
Has he decided which offer he is going to accept or is he still sitting on the fence?
5) Find Your Feet-to become familiar with and confident in a new situation-
Did it take you long to find your feet when you started your new job?
6) Lose Your Touch-to no longer be able to do something as good as you could before-
He was once a great player, but with age, he has lost his touch.
7) Stab Someone In The Back-betray someone-
He had been lied to and stabbed in the back by people that he thought were his friends.
8) Wear Your Heart On Your Sleeve-to make your feelings and emotions obvious rather than hiding them-
You always know where John stands because he wears his heart on his sleeve.
9) When Pigs Fly-something that will never happen-
He plans to clean his house every week, but he will probably do it only when pigs fly.
10) A Chip On Your Shoulder-an angry attitude from someone who feels unfairly treated-
She's not going to make any friends if she walks around with a chip on her shoulder like that.
11) Lock The Barn Door After The Horse Has Bolted-take precautions after damage has occurred-
After the burglary they installed an alarm system. No use locking the barn door after the horse has bolted.
12) To Be At Large-free, uncaptured-
Twelve prisoners are at large following a series of escapes.
13) Rain Cats And Dogs-rain very heavily-
It was raining cats and dogs, so all flights were cancelled.
14) Rack Your Brains-put great effort to think of or remember something-
The detective kept racking his brain to solve the mystery when his eyes got stuck at the evidence kept on the table.
15) Ray Of Sunshine-someone or something that brings hope into the lives of others-
Her students proved to be ray of sunshine for her when she was was trying to cope up with her illness.
16) Running On Fumes-to continue doing something even when you have no energy left, to operate with low resources or money-
After having partied late into the night, he was running on fumes the next day at work.
17) Rule Of Thumb-a general principle that comes through experience and not any scientific means-
A good rule of thumb is to add the ingredients when the water starts to boil.
18) Ring A Bell-to awaken a vague or indistinct memory, something that sounds familiar-
The place he was talking about rang a bell but I couldn't remember where I had read about it.
19) Quantum Leap-to make a significant improvement or dramatic advancement-
The election of a female Prime Minister is a quantum leap forward for equality in humanity.
20) Paddle Your Own Canoe-to be able to act without having to depend on anyone-
She is a strong woman and can paddle her own canoe without having a man in her life.