The best place to begin understanding idioms is to look at the origin of an idiom.
Bang for the buck, is an idiom that reflects the amount of value you can get for the amount of dollars you have shelled out. The same bang (item) for less money would be the typical approach when shopping for the identical items. Going to five different stores for the identical item might yield five different prices. If you purchased and paid the least amount of money possible, you have gotten the most bang for the buck possible for that item. The “bang” is a metaphor for reward, return, value or best priced item. The “buck” is the dollar amount paid.
Imagine a very large firecracker you purchased for $ 1.00 and a small firecracker that you paid the same amount. When you light the fuse on the larger one, that bang (sound) is just, ok. Next, you light the smaller firecracker and to your surprise, the sound is amazingly loud. The best bang for the buck is the smaller firecracker. After all, you are looking for the loudest noise when you are buying firecrackers and is irrelevant to size. Remember, dynamite comes is small packages!
Why do we call the United State Dollar a buck? Back in the history of the US when the territories were being settled it was common place for the settlers to hunt deer, caribou, elk … etc. They would eat the meat and use the skin or hide of the animal for making clothing and blankets to protect themselves from the weather elements such as rain, snow and the bitter cold. So why the buck? Buck is the name of a male deer. The settlers that needed supplies like bullets, gun powder, boots, services and anything else they were unable to make themselves, had to be purchased or traded for. Since there was not a standard currency available in the most remote regions of settlement territories, settlers would trade buck skins (animal skins) as a form of payment or barter. The trading post would then ship the skins and furs back to the East coast of the US for use in manufacturing items for retail purchase.
Understanding the above is an example why Native speakers understand idioms. Through the educational system and acquisition at a young age, makes idioms a piece of cake. This type of background information is what we’ve learned growing up and makes for a natural foundation in understand metaphoric and term meaning when using idioms. I do not ever remember learning about idioms in school, but instead by learning through acquisition.Teachers never asked us to remember the numerous idioms. Idioms were learned by hearing adults use them. It goes full circle as my example mentioned above. If you have an expanded vocabulary you can more easily navigate idioms and comprehend the context of use, however the metaphoric meaning use can trip up even advanced learners.
I think the most daunting task for ESL learners is not to get stuck on an unfamiliar idiom expression during a conversation or when reading. Allow it to go over your head to get past the idiomatic word or expression and understand the context for communication of its global meaning. Try reading between the lines, it has been my experience in the classroom that most student have a sixth sense of whether something expressed is negative, positive, personal, spoken in jest or in being serious.
Example; if an American is smiling and or laughing then it is not to be taken as serious and anything spoken, I mean anything is posed with the intent of humor or maybe pulling ones leg.
The disadvantage to English learners is that as native speakers, we discount idioms as anything other than normal communication, since we have had a lifetime of practicing them. At the same time we can communicate without them, it’s our language’s bread and butter. We sometimes find that people who do not use them as perhaps tip toing through a minefield in hopes of not hurting themselves by an idiom exploding out of their mouth. Well it is hard to do and very boring for the person having to listen to the black and white noise of such a colorful language. Idioms are about timing and appropriation. If students try to use them incorrectly and or too often, then it can be conveyed as a form of shtick.
ESl learners have to realize that you can ask your instructor to teach you all the possible idioms recorded throughout history. It is better to put the ball in his court by asking your instructor to use the common idioms at every opportunity during lessons and conversations in and outside the classroom. This will give students a chance to look past an idiom and draw their own conclusion about its relation to context. Students should out of the blue ask their instructor the meaning of the expression and what similar idioms can be used in place of the topic expression. American idioms are a dime a dozen with several idioms that mean the something can be interchanged, e.g. … busy as a bee, busy as a beaver, working like a dog or working your butt off … etc.
Most importantly while you have spent an arm and a leg on a crash course learning and improving your English skills. Try and practice speaking English at every opportunity in and outside of the classroom. If you bolt out of the classroom and revert to the use of your native language for communication, sooner or later you will realize missed opportunities to refine your skills taught in the classroom and one less chance for a feather in your cap. Students need to go all in and immerse themselves in English to get a return on their language investment.