Standardized Testing
Love it or hate it, you'll likely do it at some point. Read some tips below and find other sites to help you better you're ability to take college entrance exams.
SAT Prep
One of the best ways to study for the SAT. Free, simple to use, endless questions, lessons, and videos to help walk you through example questions. Very helpful to get to a high score, but limited for 1500+.
Bluebook Practice Tests
If you're going to take the SAT, it's more or less a must to take at least one of these. They're free, the format is the exact same as you'll see on the real test, and the question difficulty is just slightly easier than the real deal. Practice tests 1-4 are generally considered easier than 5-10, so use the latter for a better comparison for what your test score will look like. Make sure to go over incorrect answers and use it as a learning tool.
SAT Prep Books
There's a wide range of SAT prep books available anywhere; Barron's, College Board, Princeton Review, and Kaplan tend to be the most popular options. Make sure to do your research to pick the best option based on how you learn. While all these books are going to make you pay up, libraries and used book stores likely will have prep books available, and some public libraries might have the newest versions available as well.
Studying tips
Know how to use Desmos. Much of the SAT is centered around time management, and in a stressful situation like the second math module, doing all the work by hand or your handheld calculator just won't cut it. For the reading section, master the grammar and "a student has taken the following notes" questions. These make up about half of the reading section and are much easier to get a decent mastery of in comparison to passage reading and vocabulary questions for most people.
Online Help
ACT Prep
Many of the same qualities of SAT prep books apply to the ACT as well, but a small limitation is that you will likely find fewer ACT prep books at local libraries in comparison to SAT prep books. If you're looking for what to get, Kaplan is the official partner for the ACT and will likely have the most comparable questions and style to the real deal.
Youtube/Social Media
It might seem crazy, but if you're in a time rush or on the go, there's an almost unlimited number of videos to get some quick knowledge down, or longer videos if you need help on a difficult topic. Just make sure to try and find reputable channels or personalities and make sure you're able to focus without getting distracted easily.
Tutoring
While it will often be the most expensive studying method, tutors can help you one-on-one and give you instant help for what you are struggling with. Make sure you maximize the effectiveness of having a personal tutor since many of them have an extensive knowledge of the topic and can help only when you ask.