The Idioms Collection (VI)

At The Drop Of A Hat: 
Willing to do something immediately.

Back Seat Driver: 
People who criticize from the sidelines, much like someone giving unwanted advice from the back seat of a vehicle to the driver.

Back To Square One: 
Having to start all over again.

Back To The Drawing Board: 
When an attempt fails and it's time to start all over.

Baker's Dozen: 
Thirteen.