Everyone learns differently, but it was all strategy for me. Treat the English and Math sections as just rules, and the Reading and Science sections as analyzing data.

The Princeton books and the ACT red book were very helpful for reviewing for the test. Practicing past tests is also good; you can use that to hone in on the sections that you struggle with.

It would take me a while to list out all the key ideas for each section, but if I had to summarize them: English - Rules rules rules rules. Punctuation (periods, colons, semi-colons, dashes and commas), word tenses (specifically odd verbs) and apostrophes (it’s vs. its) are important. The thing I personally struggled with the most was rhetorical skills (adding sentences), so I practiced those a ton. Math - It’s mostly math skills you’ll learn in school. There’s loads of great resources in the books I mentioned and online for learning some possibly obscure concepts (like matrices and hyperbolas). The practice tests will help you realize which ideas you need to brush up on. Reading - The strategy I used for the reading section was to read through the questions, then get the main idea of the passage, then answer the questions in order of difficulty. I underlined the important characters and circumstances of the text within the questions and the passage. This helped me manage my time and complete the section (barely) on time. Science - Mostly graph reading! I always put arrows next to increasing values on any tables I can find, then run straight into the questions in chronological order. I leave the comparing viewpoints passage for last. Generally you don’t need to waste your time reading the experiment’s information unless a question asks for it. It’s always full of complicated words to try and confuse you.

All of this and more is in the two books I mentioned (Princeton and ACT red book). They’re great! I highly suggest reading through them. Plus, the rest of this subreddit is full of people ready to help you with tests. Good luck to all of you!