In order to start studying Korean well, you're going to need a good phrasebook. Here are 7 that are freely available online:
The following 3 phrasebooks and guides introduce the basic necessary phrases
for most aspects of life in Korea. They are the best place to start.
1. The National Institute for the Korean Language Phrasebook
2. Life in Korea Phrasebook
3. Wikitravel's Phrasebook
Slang & Street Korean
Some of the following 3 contain vulgar expressions. Use at your own peril.
There are indeed very many useful casual and slang expressions that can be used with your friends on a regular basis. But, the two books below also contain a chapter of two on the "dirty" stuff that you'd see in R-rated movies. But I figured, it's useful for understanding Korean more regardless or whether or not you actually use the phrases.
4. TOPIK Guide Slang and Proverbs
5. Making Out in Korean Phrasebook
6. Dirty Korean Phrasebook
7. Smartphone Phrasebook by Cogent
This app is a free download, but doesn't include all the content for free. A total of 6 sections
are available in the "Lite version" and you can upgrade to the full 18 sections
(including Tongue Twisters) in "Pro" for around 5,000 won.
Do you own any of the above phrasebooks? Which ones do you find most useful/promising?