Here are some tips I got a hold of, they might help you too:
1. Question stems: Read the question stems before investing any time in attacking the passages. This will allow you to pinpoint exactly what you're looking for as you read, saving you a considerable amount of time.
2. Watch out for "Out of Bounds" choices: If several choices appear to be true, see if they pertain to the question itself and to exact boundaries of the argument. Many, many times, multiple answer choices will be true, as far as they go, but the incorrect choices will fall outside the relevant boundaries.
3. Assumptions Rule of Thumb: When working on assumption questions, remember that assumptions, upon which a conclusion relies, must be true for that conclusion to hold. If you have any doubts about whether or not the conclusion relies on a particular assumption, assume that the assumption is false. Is your conclusion still true? If not, the conclusion does rely on the assumption in question.
4. Diagram the Argument: know the basic functions of the following in an argument.
a. Claim/Hypothesis/Conclusion - the idea that the argument attempts to support; note that the hypothesis will likely be backed by data or evidence in order to arrive at the conclusion. (The conclusion is a hypothesis bolstered by evidence and in that way is proven true.)
b. Assumption - a statement that must be true in order for the conclusion of the argument to hold.
c. Evidence - information used to back up assumptions and the conclusion.
Don't focus too much on consciously diagramming the argument, but do make a mental note of the different functions within an argument as you tackle questions.