I did very well on the vocab section the first time I took the PCAT, so I'll help as best as I can.
1. When you get your quiz score back, do you get to see an explanation for all the answers you got wrong? If so, go back & read the explanations very carefully, reason to yourself WHY they're right.
2. The people at Kaplan probably already told you this, but get use to looking for key words in the sentence (mainly conjunctions) that tell you the LOGIC of the sentence. Words like "but," "therefore," "and," "despite," are really common... they practically tell you the relationship of the blank words.
"Even though Klara was extremely confident before exam due to her ______ studying, her test score was surprisingly ______."
KEY WORDS are "even though" (the "surprisingly" just reinforces it). What is the inherent logic saying in that sentence? Think about it BEFORE you even look at the answer choices... you need a synonym for "rigorous" for the first blank, and a synonym for "poor" for the second blank.
3. Also, never give up on a question b/c you don't know the meaning of a word... you can almost always get it right based on elimination & logic. This is particularly true when there are 2 blanks!
4. Finally, MEMORIZE VOCAB. There are a lot of obscure GRE words on this exam. I recommend the Kaplan GRE Verbal Workbook for all of your verbal studying (check on Amazon.com).
GOOD LUCK! =)