I just took the ACT, and I got a 36 on Science. Basically, it's testing how well you can look at tables and graphs and use them to answer questions, so it doesn't matter whether or not you actually know anything about science. Therefore, my strategy is to ignore all the written portions and the tables/graphs and simply skip to the questions. Then, I look back at the table the question references and find the correct answer. This allows me to save time (if I remember correctly, you have 35 minutes and 7 sections, giving you only five minutes per section, or not nearly enough time to actually read through everything).
The tricky section is the one with the two or three selections of people who suggest different explanations for the same phenomena. The reason this section is tougher is because you actually have to read it in order to answer the questions. However, if you do the other six sections quickly enough using my method, you should have plenty of time to try to answer the questions in this section.
I hope this helps.