These are the resources I use:
For the SAT
1. Bluebook® Testing App
The College Board has released 6 official practice exams on its Bluebook app. These are your best guide to what the SAT looks like.
2. Nonadaptive SAT® Practice Tests
These practice tests are meant for students who need to take the test on paper. The majority of the questions on these tests overlap with those on the Bluebook tests (so do the Bluebook tests first). That said, these tests have many tough questions that aren't found in the Bluebook tests, so they're worth doing for the additional exposure and practice. I recommend printing them out and doing one section at a time. Don't worry about whether you've seen some of the questions before. In my 15+ years of teaching, no student has ever had a perfect record when it came to redoing practice questions they had already seen and studied (oftentimes just the week before). The key to learning is repetition, repetition, repetition.
3. The College Board's Educator Question Bank
The College Board offers a question bank that includes all the questions from the Bluebook and the Nonadaptive Practice Tests as well as hundreds more. If you're saving the official Bluebook tests for later practice and don't want to see questions from those tests (or if you've already done them), the question bank allows you filter them out. You can also filter by difficulty and topic to focus on the questions you personally struggle with.
4. Anki
SAT vocabulary is back, both in the sentence completion questions and in the reading passages.
With Anki, it's easier than ever to improve your vocabulary. For those of you who haven't heard of it, it's a free flashcard program that helps you memorize words through spaced repetition. For long-term memorization to occur, our brains need to have repeated encounters with the vocabulary we're trying to memorize. Science has shown that the best time to re-encounter a word is just when we're about to forget it. Hence, spaced repetition.
By using the program once a day, Anki's algorithm will track your memory and adjust to you. Words you struggle with will show up more frequently while words you've mastered will show up much less often. Anki gets rid of the hassle of physical flash cards and speeds up memorization significantly. A few students of mine have memorized thousands of words with amazing retention.
To learn how to setup Anki for SAT Vocabulary, check out my 10-minute Anki tutorial.
For the ACT
1. The Official ACT Prep Guide
Also known as "The Red Book," this is the essential book for ACT Study. It's released by the official test-makers and contains 6 practice exams in the book and 3 more you can access online.
2. Free ACT Practice on the ACT website
Scroll down to the heading "Free ACT Test Subject Practice Questions" to find what is essentially another practice exam (e.g. the "ACT Math Practice" link goes to the math section of the practice exam).3. Past ACT Practice Test Booklets
These are official past exams that the ACT distributes each year to students. You'll notice that not all years are listed because some years are repeats of a previous year. I've sorted through them all and I've compiled a unique list below: