Vocabulary Myths: Applying Second Language Research to Classroom Teaching by Keith Folse (2004, University of Michigan Press) is a great introduction to the gap between practice and research in vocabulary learning and teaching.

I highly recommend the book, but if you’d like a shorter summary, Folse’s article “Myths about Teaching and Learning Second Language Vocabulary: What Recent Research Says” [TESL Reporter 37,2 (2004), pp. 1-13] is also available if you have access to online journals.

The eight myths are:

1. Vocabulary is not as important in learning a foreign language as grammar or other areas.
2. It is not good to use lists of words when learning vocabulary.
3. Vocabulary should be presented in semantic sets.
4. The use of translations is a poor way to learn new vocabulary.
5. Guessing words from context is as productive for foreign language learners as it is for first language learners.
6. The best vocabulary learners make use of only one or two effective specific vocabulary learning strategies.
7. Foreign language learners should use a monolingual dictionary.
8. Vocabulary is sufficiently covered in our curricula and courses.

Think about your language classes and how many of these myths were prevalent in the textbook or even encouraged by your teacher.  These myths make teaching languages as well as designing textbooks much easier for the teacher or author, but they go against second language acquisition research on how learners should go about learning a language and tend to make learning even harder.