I got a 520 with a 131 in CARS, not perfect, but not too shabby either. For CARS I would read the whole passage and try to deeply understand the main argument, themes, and content of the passage before going to the questions. I would always try to keep the main message of the passage in mind when answering the questions and I spent about 5-6 minutes reading the passage.
For all other sections I always read the question first, figured out quickly if it was a passage based question or a pseudo-discrete and then read the passage to look for the appropriate information. Sometimes passage questions are "pseudo-discrete," meaning they don't require any passage information to answer; if you have memorized the appropriate content, it's a freebie. Other questions might require you to find interpret a graph, find a specific sentence that tells you the name of an enzyme, etc., within the passage. Thus I always thought it was more efficient to read the questions first and work backwards.
All this being said, you have to experiment a bit and figure out what strategy you are most comfortable with and what works best for you. There are many ways to skin a cat.