I've got one of those GRE study guide prep book things and they have a wordlist of 3500 words that I should know. The breakdown is something like this:
50% are words I already know and use in my daily hooplah
10% are words I already know but I don't use them
10% are words I recognize, but couldn't tell you the definition if you asked
That leaves 30% of the words to learn. Course, that's like 1000 words so I decided to put all the ones I didn't know in a wordlist file and wrote a cgi script to pull up a random word from a random wordlist (the 3500 words are broken down into 50 or so wordlists) and give me the word and definition. I figure I'll start using them in emails and other digital correspondence and that way I'll cycle them into my vocabulary.
Feel free to join along in this little game of mine. It's a game I like to call, "I don't want to be studying--I want to be programming".