Here's a list of the 6,000 most common words in Korean, hopefully it should keep you busy for a while: http://www.topikguide.com/2012/08/6000-most-common-korean-words-1.html I also highly recommend talktomeinkorean.com for audio lessons.^^

A strategy that you can use is by simply attempting to translate from Korean to your mother language. So take an excerpt from a book, news article, magazine, etc and translate it. Whatever words you don't know, highlight them, then look them up, and write down the meaning. Naver.com has an excellent online dictionary from Korean to English and vice versa. To get to the dictionary, when you arrive at the home page, in the green bar, click "더보기" then in the second column, 8th word down, you'll see the word "사전," which means dictionary. Click that. Search using the left hand bar in the center of the screen, with the "어학사전" above it. That'll give you accurate English 99% of the time. Don't look up entire phrases, because it gets less accurate as you do that. If that site is down, you can also use Daum.com. It has a pretty good dictionary too.

You can use " www.memrise.com ". It has many courses for Korean and it's really amazing. ( courses for phrases, verbs, words, etc. really great! )

Wow, I had not seen that before! Thanks. :D

Jonathon gave you a good vocab list. For actual help memorizing the words, I would try memrise.com - it's pretty amazing.