Physical sciences and Biological sciences
I am going to handle these together because I tackled them the same way
There are 52 questions in each section and about 8-10 are free standing questions without a scientific passage associated. With these free standing questions - you will either KNOW or NOT KNOW the answer to them. NEVER spend more than 1 MINUTE on each of these questions. These few questions are meant to test general knowledge and conceptual facts about their respective sciences. With that being said - I would answer these questions first. I would skip through the test's passages, find these questions, and answer them as fast as possible. If I was unsure, within 30 seconds, I would mark it for review. I practiced this way, and it was the best improvement I made to my test taking strategy because by test day I could finish these questions in 3-5 minutes.
This left me with PLENTY of time to go through the passages.
With the free standing questions out of the way, I was left with over an hour to read the passages - this made it much easier to finish each section on time. I would read each passage as quickly as possible, highlighting each passage minimally. Then I answered EACH question with what I thought was the right answer. If I was in doubt, I still answered, but I then marked it and moved forward. Once I was finished answering every question in the section, I would spend the rest of my time reviewing/re-answering my marked/checked questions. I would unmark/uncheck the questions I didn't change the answer to.
Essentially when I reviewed my questions - I tried to use the passage and the question prompt to ARGUE my "gut feeling" answer.
Thus, when I submitted the section, I would submit it with only marked questions that I was truly unsure of. This proved valuable for two reasons - 1. It allowed me to submit a test that really gauged my knowledge and 2. When reviewing the practice tests, I could go through with my books and look up the information for the ones I had marked. I made sure I understood WHY the answer was correct, not just see what the correct answer was. I would then work through the question again if it was a math based question.
When you first start taking practice test, you will have a lot marked when you finish. However, as your studying continues and your knowledge base grows, you will mark less and less.