Vocabulary -- What is it Good For?

Absolutely everything.

(On a side note, check out this hilarious clip from the movie "Rush Hour," starring Jackie Chan and Chris Tucker, in which the classic 70's urban protest song "War" is playing in the background. And while you're on YouTube, take a look at the music video of the song, from 1970, to understand the historical and cultural context.)

Unlike war, vocabulary is good for absolutely everything. Perhaps your most important task as an English learner is to build up your vocabulary. A limited vocabulary will hold you back, and prevent you from understanding and speaking English effectively.

Developing your vocabulary is time-consuming, but, unfortunately, there is no shortcut.
Although it's true that you will acquire new words just by hanging out with native English speakers, or even by watching TV, you must continuously learn and use new words until you reach a level of fluency. Using new words (speaking, writing) is the surest path to total acquisition.

Did you click on the link just above, on the word shortcut? It's linked to http://www.thefreedictionary.com/. I recommend bookmarking this site, the best online English dictionary I have found. Not only does it provide excellent definitions, but it also allows you to hear how the word is pronounced. You will also find translations in your native language.

Now I have two words for you when it comes to learning vocabulary: flash cards. There is no better method. Word lists are also good, but flash cards are better.  After making a flash card, start learning the word. Keep at it until you've learned it. When you've learned a word, put the flash card away --you won't need it anymore. Try your new words on friends and teachers -- they will be suitably impressed! Use new words in conversation whenever you can. Practice saying them out loud to yourself and others. And if you forget the correct pronunciation, ask a native speaker, or find the word on http://www.thefreedictionary.com/ and play the audio.

Technology -- you gotta love it. Wish I had the Internet when I was a student. But sometimes low-tech is the way to go. And you can't get more low-tech than a 3'' x 5" index card and a pencil.