Well, I don't know about other methods of expanding vocabulary. I was told that you should write down the meanings of words commonly used in english newspapers and then read the papers regularly and these words would often be used repetitively and hence you would memorize them easily. For me, this method worked as my vocabulary was enhanced considerably.

However, when it came to the difficult words as given in various tests, it was partially successful. I tried cramming such words, but it didn't work. Remembering such words is indeed a difficult task, and if you do the cost-benefit analysis in terms of the time used in remembering such words and compare it with doing some other tasks. Then my experience is not to remember or cram such words. You can utilize that time for other tasks. This is my personal experience. Maybe there are people who may have other views.