I often tell my students that one of the few useful things they will do while preparing for the SAT (or ISEE or SSAT or GRE, for that matter) is to improve their vocabulary. In other words, when all is said and done, and they have test scores that they're happy with, most of what they've learned in the process of preparing will do them little good in life or in their studies until, of course, they next have to prepare for another standardized test. But an improved vocabulary can and will continue to help them, both in school and, most likely, professionally.
The question quickly becomes, then: how do I improve my vocabulary?
I think almost all of us have, at some point, crammed for a vocabulary quiz. You sit down with your list of twenty words. You quickly winnow out (there's one for you!) the five you already know, then you just read the other fifteen and their definitions, again and again, perhaps with the aid of flash cards, until you "know" them. The next day you regurgitate them on your quiz. Two weeks later, you haven't the slightest notion what any of them mean.
Why does this method succeed in the short term, but fail in the long term? Because our long term memory is associative; we learn new information best when we can connect that information with something we already know. Traditional methods of cramming for vocabulary tests-- things like flashcards-- involve taking a word you don't know, and associating it with a definition you also don't know. They give our long term memory nothing to hold onto.
So, then, how do you learn vocabulary? By coming up with ways to aid your brain in making those associations, thereby retaining the new words as you learn them. Here are a few of the best ways to do this:
This is actually probably not the best way to learn a lot of words in a few months. But it is almost certainly the best way to improve your vocabulary. Read books (or magazines or websites) that use challenging vocabulary, and-- here's the kicker-- actually take the time to look up the words you don't know. The context of the reading itself will help make the word easier to learn (assuming it's been used correctly!), and will help your brain to form associations.
The only downside to this method, really, is that it's a bit haphazard in terms of the exact words you'll end out learning. But frankly, it's pretty hard to predict the exact words that will show up on your test, so nearly any expansion of your vocabulary is potentially useful.
If you want to add a bit more structure to the simple advice of "read more and look words up," add those words you learn this way to a vocab list, include something to help you remember the context (more on that below), and revisit the words periodically (more on that below, too!).
Associate New Words with Things You Know
So you have your list of 250 or 500 or 1,000 words to learn. You sit down and you start to make flashcards (or you just sit down a start to pore over the list). How do you make those words more memorable?
You make associations.
There are lots of ways to do this. You can associate a new word with a person or character. So "precocious" might be associated with Stewie from Family Guy (though if you make him precocious, don't also make him malevolent); "reprobate" might be associated with Lindsay Lohan (though then you wouldn't also want to make her cosseted). And so on.
If you're more visual, you can associate words with pictures, or even movies or videos. Some sites (like vocab videos) do a pretty good job of this, though you may find taking a more personalized approach (e.g. finding pictures for yourself that work with a given word) works better.
Sometimes, writing a good sentence can help, too. For example, my father loves oysters, so I might make the sentence "Dad has a prodigious appetite for oysters" if I wanted to learn prodigious. People often tell you to make sentences, but the key, as always, is that the sentence ought to have meaning for you, and be memorable to you, otherwise it's really a waste of time.
Sometimes you'll just find odd things about the words that make it memorable; for example, for years I had trouble recalling that "vituperate" meant "to use harshly condemnatory language;" then I saw the word "viper" in there, and I've never forgotten since.
Use your Languages
Most complex words in English came to use from Latin, usually by way of Middle French. This means that a lot of our more complicated words have strong Latin roots, and you'll often find that you can recognize those roots if you study any Romance language (Spanish, French and Italian being the most common). For example, you may not know that "arboreal" means living in trees, but if you know that "arbre" in French or "arbol" in Spanish means tree, it makes the word a lot easier to learn. Then, when you seen an arboretum mentioned elsewhere, you'll probably be able to (correctly) guess that that has something to do with trees as well.
Don't Rest on Your Laurels
Just because you know a word cold now doesn't mean you'll still remember it a month from now. Return regularly to the words you've learned (complete with associations, images, roots, and whatever else you've done to make them memorable) to make sure they're still in your head. If you still know the word, you can make the next check-in a little later. If you don't know, reduce the interval before the next check.
So to sum up: read more, make strong associations, and keep checking in to make sure the words are sticking in your brain, and your reward will be better test scores and a better vocabulary.