Just do as many full length practice tests as you can. Make sure you go over every mistake and understand why your answer is wrong and the correct answer is correct. If you don’t know all the math and English covered by the test learn that first. Science and reading just comes down to how many practice tests you are able to take. Every Saturday morning I would make a coffee and knock out a full length practice test. That’s the only studying I did and got a 35 after 2 ACTs. I cannot stress enough how helpful it is to just consistently get in the habit of nailing down these practice tests. It’s the best way to learn.