I would like to know more about how to say things correctly, or more accurately, using the expression of my Mexican listeners. For example, for caer: "El avión cayó en el océano. The plane fell into the ocean." I would not say the airplane "fell" into the ocean, I would say it crashed into the ocean. So should I use "chocar"? What is the common way to express that idea? And how can I learn those common expressions that do not translate exactly?
In the above example, I assume you are illustrating variations in the use of caer. And while I understand I could say "fell," that really has a different meaning. If an airplane was on a boat (barge), I might say it fell off, or rolled off the barge while it was being transported. But if the airplane was flying and had an engine failure, and landed in the ocean, I would say crashed into the ocean.
Following is my answer; feel free to follow the link to the "Readers Respond" page to suggest answers of your own:
Answer: Obviously, the best way is to become so familiar with the language that things "just sound right." Easier said than done! And, of course, if you know a native speaker, it never hurts to ask. I've done that frequently while traveling, even asking restaurant servers and hotel clerks what is the best way to say something. Few have seemed to mind.
Other than those options, not always available, one thing that I do when I want to find out that sort of thing is to perform Google searches in Spanish (with advanced preferences, you can narrow the search to Spanish-language pages) to find out how native speakers refer to such things.
In the case at hand, you could try the search "avión * océano" (with the quotes) ? that's a way of looking for pages that have the words for airplane followed by the word for ocean with unknown words in between, and then looking for places where the idea is conveyed of a plane crashing into the ocean.
In this particular instance, as it turns out, I found far more results that used caer than chocar (although I did find one reference to a plane that "chocó contra la superficie oceánica").
Another method I've found useful is to find the English-language Wikipedia page that covers something you're interested in talking about in Spanish. On the left side of most pages, you can click to the equivalent pages in other languages ? not a translation of the English (well, sometimes it is, but not often), but an independently written work. I don't trust Wikipedia as an authoritative source, and it should never be used as a reference in an academic work, but I have found it is pretty good for seeing how native speakers say things. This is really useful when getting into subjects that have jargon and/or other words that aren't in a dictionary.
For this particular topic, I went first to the English page "List of accidents and incidents involving commercial aircraft" and then clicked on the Spanish link to arrive at the page "Anexo: Accidentes e incidentes notables en la aviación civil." Skimming through that page, presumably written by native Spanish speakers, I found the verb caer used several times to refer to planes that crashed into bodies of water. I also found several cases where the verbal phrases estrellarse en or estrellarse contra were used. (Estrellar is commonly translated as "smash.")
This may not be a perfect way of finding out what is the most common way of saying things, but it does tell you that neither caer nor estrellarse would stick out as being something that only a foreigner would say. This quick research suggests that either verb would be fine to use.