I’m a sophomore in high school and took the ACT for the first time and I got a 34 (in all honesty I did not study once, but I am also not trying to brag whatsoever, just saying for the sake of the question) - 36 in Reading, 34 in Science, 32 in English, and 33 in Math. This puts me in the 99th percentile. However, my writing - an 8 on the new scale - is the 82nd percentile. Is it worth taking another ACT to raise my scores, and if so how difficult would it be to do so? Also, how many hours total is a good amount to study? And will my much lower writing score hurt my applications?
i mean, most colleges don’t even ask for the writing portion, and if they do, i don’t think it matters, really. your 34 is great. i wouldn’t take it again.
I agree. Schools don’t look at the writing score. I don’t see why you would even think about doing it again. Work on other parts of your application with your free time 
Are you applying to HYPSM? Many of them do want the essay on your ACT or SAT. I would check your particular schools’ requirements. Most schools do not require the essay portion. If your list of colleges that you’re applying to doesn’t care, don’t bother to retake the test.
I got into the University of Michigan- Ann Arbor OOS (which requires the essay portion), with a 34 composite and a 7 on writing. You’re fine. Unless you are specifically majoring in language comp, they are not going to look at your writing score. They will read your writing in your admissions essays, so if those are well-written, you should be in good shape. Good luck!
The most effective studying is taking a practice test and writing down, on flashcards, what questions you got wrong and what type of questions they were. Then, study what you got wrong for the week as well as just doing SAT KhanAcademy prep.
Next is methodology: I’ve gotten 36s on my last two practice tests; today was the first ACT I took. What I would do to prepare is get a math study guide and religiously memorize the formulas. For Writing, get an english study guide and memorize the tenses, possessives, who/whom. For Reading, get an AP Language study guide and practice reading argument essays. Science is just reading comprehension and good time management. Science also has the most trick questions: read very carefully. In order to have enough time to read carefully: first read blurb, underline prompt in questions, then reference the passage and underline whatever is informational. Repeat until you match the graphs/text with answers.