One of the best ways to improve your vocabulary is to read books that use language just beyond your current level of vocabulary.
Find a book you like with a lot of words beyond your current vocabulary. Buy a good dictionary, and sit down with the two. When you find a word you don't know, look it up. Find excuses to use the new words of which you have become most fond.
Titus Groan by Mervin Peake has TONS of words with which I am not familiar. It's an English, gothic, dark fantasy book with a lot of brilliant imagery and humor in it. Don't know if that's your thing, but if it is a good place to start.
Also, finding friends with an expanded vocabulary (professors, college students, people at coffee houses) helps a lot, too. Just ask them what they mean when they say words with which you are unfamiliar.