Here's my thoughts on learning vocabulary: http://www.italki.com/discussion/91279
I love the Korean Grammar in Use series of textbooks. You can purchase them from amazon.com.
I also adore these books from the Korean Ministry of Education designed for Koreans living outside of Korea. You can view them online for free here: http://www.efka.or.kr/user/info/data.asp?leftNum=1
Other than that, I like talktomeinkorean.com and howtostudykorean.com.
endic.naver.com is a great dictionary, and naver.com itself is an awesome resource. I do occasionally use dic.daum.net too for a dictionary. Then, more generally, there's youtube.com, italki.com (hehe), lang-8.com, and tumblr.com (and other blog sites). There's Monash University's site too. Also gobillykorean.com.
Here's some free, older, online books too: http://www.koreanlab.co.kr/main/index.asp?t_id=1
Quality over quantity^^
Also, fluent in three months talks about language learning.

You need lots of practice and exposure!!
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Start by learning the writing system and pronunciation and sounds.
Then learn some simple expressions while you begin to simply learn everything^^ Simple grammar and vocabulary. Practice reading, writing, speaking, listening, typing, and conversing, and learn about the culture. I personally believe it's important to understand the basics of the grammar of your own language too.

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Feel free to ask me questions or for corrections :) 

I will do my best to help.

Hey guys, i’ve been using an app to learn Korean and it also looks so cute! It's really useful and helps you to learn Korean. Check it out at https://play.google.com/store/apps/details?id=kr.eggbun.eggconvo