I've tried reading the passage first, and I've tried skipping straight to the questions. I got the same score with both strategies (26, but I'm hoping for a 29+). Which strategy gives me the best chance of improving my score next time?
I'd recommend skipping straight to the questions on passages that involve visual data interpretation. In these situations, it's easy to answer questions by simply looking back at the charts and graphs you're given.
For the conflicting viewpoints section, on the other hand, I'd recommend skimming each passage first and making a small note of what the main argument is. It's harder to skip straight to the questions on this part of ACT Science because the answers aren't readily available based on visual aids. I'd also advise you to save conflicting viewpoints for last; it can be a little disorienting in the middle or at the beginning of the section because it's so different from the rest of the material.
Here are some more tips for ACT Science if you're interested!