Kate,
The temptation is to spend too much of your valuable time reading and then re-reading the entire passage, in an attempt to ensure that you fully understand every dot and tittle before you move on to the actual questions.
Some of the passages are very long, and not every single line or word will need to be analyzed in order to answer the associated questions.
Therefore, it might be advisable to scan the questions really quickly (noting key words and phrases mentioned), then carefully read through the passage ONCE from start to finish, to get the overall context. Later, as you work on each individual question, you can refer back to one specific section, to analyze the meaning of the word, phrase, or sentence they are alluding to in the question.
This strategy certainly worked for me, and Lee too (hopefully). It's a compromise between not reading the passage at all (very bad), and spending too much time reading the passage (also very bad)...
If you have already developed a strategy that works, stick with it. If not, this strategy may prove helpful to you once the clock starts ticking.
Best of luck,
Snazzlefrag