Graded readers and idiom glossaries

http://www.visual-idioms.com/

Ask your students to select a graded reader. You'll need to help them choose appropriate level but they should have some choice over what they will read. The higher the level, the more idiomatic language they will find in the book. Each student should have a different book (I believe most schools have a collection of graded readers). Set the time for accomplishing the task. Ask your students to search for interesting idioms and record them as they read. Ask them to include the page number (it's good if they store the idioms electronically so that they can later organize the idioms alphabetically or upload the document if necessary). They should by now know what an idiom is but make sure all your students know what to look for. Give them plenty of examples and the definition: an idiom cannot be understood from the individual meanings of its elements, and it's a combination of words that have a figurative meaning, which is separate from its literal definition.
After one week's time, for example, ask your students to bring their collection of idioms to the class. Each student will have created an idiom glossary for one graded reader, which will later help someone to read the book. Ideally, the idioms will be accompanied by a definition, translation (if possible), an example sentence, and images (photos or doodles). Some graded readers include glossaries so make sure your students just didn't copy them.

Graded readers can 1) be a great source of new vocabulary 2) help reading fluency development 3) be highly motivating for students because they are comprehensible.