It's all about quality, (and some quantity)
You've sharpened your pencils, have your notebooks and know when your SAT/ACT test is scheduled. You just have to come up with a plan. So, you go onto the internet and type in, "SAT exam prep" and Google comes back with 2,360,000 results and you sit there, stunned. Where do you start? HOW do you start? I'm here to help you with that.
First, start with the time factor. Back date from when your exam is, (here's a handy online calculator-https://www.timeanddate.com/date/duration.html). That's your starting point. Then determine how much time you can devote, per week, to studying for your exam.
Second, take a practice exam. Go to the College Board website, https://collegereadiness.collegeboard.org/sat/practice/full-length-practice-tests, and download their practice exams. Using the College Board exams will ensure you practice with the same type of questions you will encounter on your exam.
Third, come up with a study plan, based on your practice exam results. This is the point that you may, or may not, consider a private tutor. Tutors help guide you, help you stay focused and help you stay accountable. Make sure you add other practice exams, along the way.
Fourth, now that you've mapped out your study plan, STICK TO IT!!! The SAT and ACT are not exams you want to cram for. Doing a little, every day, is far better than trying to cram in a lot, in a couple days.
Preparing for these exams are about using good resources and making your time count. Stay focused, stay dedicated, to your schedule and when you sit down at your exam, you'll be ready. Good luck!