I didn’t see here any useful idea for vocabulary building.
The most helpful idea (but also a very banal and obvious one) is talking about the daily life. But it’s for beginners only. All other ideas are absolutely inefficient and merely wasting the expensive time. I think it’s quite silly to spend time for scanning pictures or talking to each other about vegetables in order to improve the vocabulary.
However I agree that these methods are really useful for conversation practice indeed.
The best way of improving the vocabulary is reading, for all time!
So, read books, newspapers and so on; and don’t waste your time with native speaker trying to make you able to read that stuff! I think the most of people care about their money and time.
Of course, the best ways to remember the words are learning words in context and; using visual associations and feelings. And there are a few smartphone and web apps allow learning words in this way. But in any way you have to read a lot to find out new words and revise them.

I contribute a tip to learn new English words. That's simple and impressing. <em>Search images of the word in yahoo.</em>

I still remeber clearly how I was shocked when searching "ugly" images. After then I never forgot "ugly".

Great article, I agree with all your suggestions, except putting away flash cards.

I agree vocab apps for phones are not helpful really, but something like Anki is really helpful. Using Anki, students can build the flashcards themselves, add notes, example sentences and even pictures and sound. Also Anki uses spaced repetition which is really helpful for optimum memory retention. I encourage all my students to use it, and they all say they find it really helpful. 

I think flashcards definitely have their place, as long as you use them to their full potential. I couldn't have got as far as I have in Chinese without flascards and Anki. I think flashcards are especailly helpful for Chinese learners as Chinese is not written with letters, you can't attempt to read a Chinese character unless you have spend time looking at it, memorising how it looks and how to write it. 

Eugene: You have a good point; reading is a great way to expand your vocabulary. Texts written by native speakers can expose you to the ways native speakers use grammar and choose their words. Quality input is especially important for effective learning. (http://homepage.ntlworld.com/vivian.c/SLA/Krashen.htm)

However, reading and writing are skills only remotely related to speaking and listening.
Consider this: when you first learned to speak, how did you learn? Did you learn your first language by reading? Your ability to learn from reading developed from your ability to listen with understanding.
As we go through our school years, we are taught to rely heavily on written material. But remember the importance of quality input? It also turns out that our brains are in such a way that some kinds of input are retained or “learned” more efficiently than other kinds of input. Research in the areas of cognitive psychology and neurolinguistics consistanly points to the primacy of auditory and visual input in the context of human relationship.

Oh dear, I’ve gotten technical, haven’t I? I’m sorry, I sort of went into lecture mode because you brought up an issue that I believe in very passionately. Well, message me if you want to discuss it further. ☺

Sometimes, my Russians speaking students wants to know a word in French and I don't always understand what they want (our common language is English). They usually hit google translate, but that brings a lot of "10 dollars words" (in French we call them "un mot à 100 $") and even then, I don't always get what they mean, so I usually ask them to give me a link to a photo on the net or to type me, in their language, the name of the thing and I do the search on google images. That works a treat! I usually end up saying "oh you mean a ...!"

I like it when student brings a prop too, like a "show and tell". Usually, you can learn a lot about culture that way! Once a student brought a 6 foot teddy bear and plonk it on her chair. That was funny!