I struggled with memorizing vocab words when I first started learning Greek. My friend introduced me to the Leitner Cardfile System, invented by psychologist Sebastian Leitner. I have used it for vocab memorization and found that it helped me. I just use index cards with the foreign word on the front and its English equivalent on the back. There are a few vocab memorizing programs that use the same method: flashcardexchange.com and Memory Lifter.
I also just found this great site which rates memorization programs.