The first thing you need to do is purchase an English-to-Korean dictionary and Korean phrasebook. There are many to choose from, and many are available at your local bookseller (Barnes & Noble, Borders or Books-A-Million). They are also available at Amazon.com and other major online booksellers. Webster's English-to-Korean is pocket sized and costs less than $10. Lonely Planet's Korean Phrasebook is another good choice, as it is handy, travel sized, and also costs less than $10.
Carry your dictionary and phrasebook with you everywhere. Read it in line at the supermarket, the drugstore, the post office. Spend as much time per day as you can familiarizing yourself with the language.
For an extra boost, purchase a basic Korean language course (most are under $25) which are chock-full of important communication guides for travelers such as how to ask for directions, how to conduct store transactions, how to order food, how to check into a hotel, and what to do if you get sick. Pimsleur's Basic Korean has native speakers record basic Korean phrases on audio cd, so you can listen in your car or on the go. Other companies who produce reasonably priced audio courses are Berlitz and Barron's.