I think the best approach is to ensure that there is variety, in all ways:

• meaning - sometimes relate words to pictures, sometimes to other words in writing and/or speaking (definitions, examples, synonyms, opposites, etc),  sometimes to sounds or music, sometimes to actions, sometimes to context (eg. after hearing or seeing the words in an audio clip or written text), sometimes not working with meaning much at all (eg. linking sounds to memory using rhymes, etc) etc.
• in isolation vs in context - sometimes exploring meaning without any co-text at all; sometimes exploring the meaning first and then meeting the word(s) in context (in reading or listening texts); sometimes meeting them in context first and then exploring the meaning; and sometimes just meeting them in reading/listening and never exploring the meaning (giving the subconsicous a chance to do the work).
• task types - sometimes really using it in tasks that mimic real life conversation, sometimes in games, sometimes in simple exercises like gap-fills and matching tasks, sometimes in just drills, etc.

I've found with ESL students and students with under-developed vocabularies, getting them to know and understand how they learn, along with helping them make personal connections to the words is most effective. I recently wrote a vocab guide e-book about this approach. I'd be happy to send you a copy to look over, if you like.

Dear njfreelancer,

Thank you for your opinion. I'd love to have a copy of your e-book. Thanks in advance

Different teachers follow different methods to increase the vocabulary of students. Down here, working professionals have a vocabulary of just 3000 words, which is shocking.

The main culprit is ego. Students passing out from convent schools have a false sense of superiority which is reinforced by their teachers. At college, the use of slang creeps in due to peer pressure.

As an English Language Trainer, I firmly beleive that a person who has an excellent vocabulary, knows when to use idiomatic phrases, is good at pronunciation and intonation, commands lot of respect and is considered to be adept in other areas also.

Increasing one's arsenal of vocabulary will take lot of commitment and dedication. Knowledge of roots, prefix and suffix helps to get a broad idea of the meaning. To take an example, any word ending with cide (suffix) can be associated with killing. Likewise, mania means madness.

One effective method of increasing one's vocabulary over a period of time is to focus on any newspaper or amagzine. We definitely come across words whose meaning we do not know. We first try to guess the meaning of the word in the context of the whole sentence. The next step is to look up the dictionary to understand the precise meaning and make a sentence using the word. This has to be corrected by a person who has an excellent command over the English Language. This process has proven to be very successful in not only understanding the meaning of the word but also its application.

While I was presenting a course to the students of translation on "Jouralistic texts" at Paym-e Noor University (so called distance education university in Iran), I assigned the students to record a short piece of news from the VOA, BBC, CNN or any other media broadcasting corporation available. They were to first transcribe, translate the material into persian ,and provide a glossary of the key words mainly used in the news (the meanings of the words were supposed to be presented in persian and suit the context of the translation work).This is how you would be able to integrate vocabulary learning into listening and translation.