How can I do well on the SAT's?

Well i'm positive I will be taking it next year (aka my junior year) i'm a sopre right now and I'm having early worries about it. Yes, I've taken the PSAT's and seen the results. I did awfully bad. My percentile on it was 32. Are the questions on the PSAT's same type as the questions on the SAT's? or are the SAT's more difficult than the PSAT's? How can I do well on the SAT's? I mean I would have to memorize every word in the dictionary to p the SAT's cuz u never know which word will come up to u in a question in the reading question and on the psat's the vocabulary words were really hard and i never heard of them before. those are my concerns.