Personally I suppose that LEARNING new vocabulary is not one of memorization only; you have to master the words as well. I LEARNT about 1500 words in about 2.5 months, using Oxford Advanced Learner's Dictionary and some word lists. I didn't have to memorise/cram that much though, just letting the words "flow" into my head.
Just want to share my OWN experience. Well, I picked up 10 random words from a list at a time, looked up the definitions and EXAMPLES in both the list and the dictionary (sometimes there are sharp differences between their explanations) and then tried to adopt it to my writing/ speaking, whatever. When going through about 100 words, I moved on to revising the 100 words preceding these words, not these words themshelves. If there were any word that I was not sure of, or completely unfamiliar with, I used flashcards (my hand-made one, of course
) Repeated this process until I could tell the meaning of a random word with confidence.
Hope this helps