"the most common idioms" used are going to depend on a lot more than simply language. Idioms come and go in different subcultures, dialects, and time-periods at a nearly unpredictable rate. Certain phrases will last for ages while others only last for a year or so. Here are, however, some useful idioms which will add a little flavor to your speech :) http://www.smart-words.org/quotes-sayings/idioms-meaning.html

Spill the beans is slang for tell us your secrets or tell us the answer. It has nothing to do with food. It is strictly slang.

thanks to all :)

The other important point to note is that it isn't slang - it's an informal idiom.

If you mean 'Is it used in England also?' , then yes, it is. American English and British English are slightly different, but we all speak English!