My daughter didn't have the best grades and knew that her ACT score had to be high in order to be considered for BYU. She studied several hours per week for several months before the test. She took may practice tests. She used two books to study. One was a book of practice questions and the other book was "Barron's ACT 36, 3rd Edition: Aiming for the Perfect Score". The barron's book included a lot of material on strategies for the test and for understanding what the test was looking for. I feel like the Barron's book was the biggest help, but the other book was the main source of her practice tests.