I realize that a number of questions regarding vocabulary questions are closed but checking the FAQ I do not see why they would be off-topic. So here goes my question:
As a non-native speaker how do you go about improving your vocabulary? I am grad student in life sciences, and do read and write a lot in English. Likewise I read non-scientific literature almost exclusively English. I realize that my vocabulary has been stagnating at best, deteriorating at worst. I would like to do something to improve the situation but not sure how.
Back when I was learning English at school, we were supposed to look up all "new" words we encounter in course literature. There were two ways we were advised; either look the word up right away when you encounter it, or underline the word and come back to it at a later time point.
I have to say I find neither of them particularly useful; looking up words in midst of reading kills the mood, and maybe I have some mild case of OCD but I can't stand looking at a page with underlined words here and there.
Are there any useful methods that you might have tried out? Oh and second question, once a new word is "learned", how do you make sure the word is not forgotten again?