I use memrise, it is a website that helps you memorize words. You might also want to dig deep into the word. This way you can lessen the times when you mistake a word for another. For example, I used to get confused between 전하다 (convey) and 정하다 (set). But I know that 전화하다 means to call and 정리하다 means to arrange/organize. Digging deep into the word also helps you memorize the word. For example, 현실 means reality. I memorized it right away because I know 현재 means present and 사실 means fact. I hope this helps a bit. :)

Try the app, Anki. There are lots of pre-made decks for Korean on there.