I would highly suggest going online and doing some practice ACT questions. The ACT is set up very differently than the SAT, and while I find it the test questions to be much easier, there is a very tight time limit. So, here are some tips.
-Bring a watch that doesn't make any noise so you can watch your time (If you have 35 minutes for a Reading test with 7 sections, time yourself so you have 5 minutes per section, move on even if you don't answer every section)
-Study the science section carefully when practicing- you don't need to know much actual science, but you need to be able to look at a graph, diagram, ect, and be able to analyze what it is saying
-PRACTICE PRACTICE PRACTICE- seriously, if you find a whole test online, sit down and do it!!! The ACT is soooo different than the SAT so you need to get familiar with it.
Hope this helps!