A hot potato
Speak of an issue (mostly current) which many people are talking about and which is usually disputed
A penny for your thoughts
A way of asking what someone is thinking
Actions speak louder than words
People's intentions can be judged better by what they do than what they say.
Add insult to injury
To further a loss with mockery or indignity; to worsen an unfavorable situation.
An arm and a leg
Very expensive or costly. A large amount of money.
At the drop of a hat
Meaning: without any hesitation; instantly.
Back to the drawing board
When an attempt fails and it's time to start all over.
Ball is in your court
It is up to you to make the next decision or step
Barking up the wrong tree
Looking in the wrong place. Accusing the wrong person
Be glad to see the back of
Be happy when a person leaves.
Beat around the bush
Avoiding the main topic. Not speaking directly about the issue.
Best of both worlds
Meaning: All the advantages.
Best thing since sliced bread
A good invention or innovation. A good idea or plan.
Bite off more than you can chew
To take on a task that is way to big.
Blessing in disguise
Something good that isn't recognized at first.
Burn the midnight oil
To work late into the night, alluding to the time before electric lighting.
Can't judge a book by its cover
Cannot judge something primarily on appearance.
Caught between two stools
When someone finds it difficult to choose between two alternatives.
Costs an arm and a leg
This idiom is used when something is very expensive.
Cross that bridge when you come to it
Deal with a problem if and when it becomes necessary, not before.
Cry over spilt milk
When you complain about a loss from the past.
Curiosity killed the cat
Being Inquisitive can lead you into an unpleasant situation.
When something is done badly to save money.
Cut the mustard [possibly derived from "cut the muster"]
To succeed; to come up to expectations; adequate enough...