I'm the first to admit my vocabulary has not grown in the last few years. I have not worked on growing it. As someone who goes on about how much he enjoys words, how important words are to our lives, i stink at learning new words to enhance my worldview. Yes, enhance my worldview. Learning a new language expands your cultural worldview. On a smaller scale, learning new words in your native language expands ways to see your own culture.
For a bit of fun, here are two videos of Conan.
Conan's Campaign to Bring Back Thrice
Thrice Returns Once More
Conan has the right idea. It seems every week there's a new word crafted that lasts about as long as a disposable cup (and i'm not talking about the styrofoam kind). For example, 'hevage' is a word created to describe male cleavage; 'facepalm' is the act of striking your face with your palm due to another stupidity; and a 'dork knob' is a short ponytail. Do we need these words? Not really.
So how does one go about learning new words? Word-a-Day Calendars?
If you'd like, yes, but a more standard answer is reading slightly above your level. Another answer is adopting a word. SaveTheWord.org lists thousands of little-used English words one can 'adopt' by pledging to use said word in everyday conversation as often as possible. I am adopting labascate, which means to begin to fall or slip. With how i walk, this will get used, i'm certain.
If you like a bit of fun to learning, try out FreeRice.com, a vocab game that donates 10 grains of rice for every correct answer. It starts out easy, then gets harder the more you succeed, until it hits upon your reading level, which is where you learn many fabulous words, like quadrennium, hydrophyte, and numismatics. I made it to level 40 without missing a word. That's right, i'm throwing down the gauntlet, to see who picks it up.
I hope i only labascate, as i invariably will, and don't succumb to the whims of gravity and introduce my face to the pavement after such an invitation for word sport. (See what a little bit of learning does?)