Students who enter the country on student visas or immigrants who want to learn American English need to take an "English as a Second Language" course. If you teach one of these courses, then you know how difficult it is for many students to grasp the meaning of so many different words and how to construct typical American English sentences. There are some additional tools and resources you can use to help your students understand Amercian English better, and become better communicators.
There are numerous flashcards out there that can help people learn, but what you really want are object or word cards that have the names of things or common words printed in your students' native tongues and then the English word for it is printed right underneath. The best sets of cards also have a phonetic spelling of the English word underneath the English and foreign language word on each card. In this way, your students can read and recognize words from their own languages, then read the English word. When they get stuck (as can happen some of the words in English because the rules do not always apply) then your students can attempt to read the phonetic spelling instead.
Online Practice English Language Tests
Since many of your students will undoubtedly be using computers while attending a college or working a job, you may as well teach them English on a computer. There are several English practice lessons you can use, as well as online practice English language tests like the TOEFL (Test of English as a Foreign Language) practice test (like TOEFL practice tests by BestMyTest). These will not only teach your students how to read, write and speak English, but also prepare them for your final exam. Passing your exam means they have proficient understanding of English and proficient speaking skills. They are ready to join a college program or get a decent job here in the States.
Video and Audio Materials
Encourage (or assign!) your students several hours' worth of listening and watching English language media each week. There are lots of video and audio materials that can teach and translate foreign tongues to English, and watching and listening are two important communication components anyway. These videos and audio tracks will teach your students to listen for familiar words that they have already learned, and learn new words that they can then ask about in class later. It is the next best thing to complete immersion and daily interaction in an English language country, something which your students will eventually have to do anyway.