What are some of the most useful idioms to learn?
You may flip through the list of idioms given on that site, here: English Idioms and Idiomatic Expressions - UsingEnglish.com
As a matter of fact, my own belief is that an idiom is a piece of culture, so wherever you go where people speak English (the USA, the UK, Australia, the Republic of South Africa, etcetera etcetera) you'll find it specific.
But maybe, there is a list of most used idioms.
Last edited by AlexAD; 06-Apr-2011 at 15:05.
Alex is exactly right, when I moved from the USA to Ireland I had to learn a completely new set of idioms. By all means, find some lists and study them (try and organize them by theme rather than just a list of crazy expressions) and have fun but the best way to find them is by reading and watching TV or films. Try and get used to recognizing one when you see or hear it and thinking on your feet to identify the context and possible meanings.