I’d suggest finding a decent SAT prep book. Learn the words slowly, perhaps around 10 words per week. Read the definitions, understand them, get to know the words; if you know a word, you’ll be able to recall its definition and spelling with greater ease.
Repetition is a very helpful tool as well. Get a sheet of paper and write down each word ten times. Use the word in a proper sentence. Leave the words alone for a few days and then grab a sheet of paper and write them out ten times each again. You could look over the sentences you wrote before or you can write new ones.
The key to remembering things like word spellings is to keep them in your thoughts and repeat them over a period of time, giving your brain a chance to absorb the knowledge and file it into your long term memory.
In addition to the above, I can’t overemphasize the importance of reading. A lot. The more often you see the words and become familiar with them, the easier they will be to recall.