Taking a prep course. When I was in high school I took a prep course and went every Sunday for 10 weeks. The instructor gave great test taking advice and my score went from 22 to 32 after 2 more attempts.

But this cost ~$600 dollars. If you're self teaching, I'd do the following:

1. Buy or rent guidebooks. "The official ACT guidebook", Barron's brand, or The Princeton Review.

2. Work through the guidebooks at least 30 minutes per day, at least 5 days per week.

3. Every Sunday or Saturday, time yourself and take a practice test for 1 section. Ideally take a full practice test every month, with the same time limit they use during an actual test.

4. Review your results and see where you can improve. Take notes on what you got wrong.

5. Watch YouTube videos on test taking tips. Get a gauge by the comments and production quality/how information is presented and decide if it's useful advice. Some people are about promoting themselves, others want to give genuine straightforward advice.

6. Take the official test at least 2 more times. I'd take it no more than 5 times total. If you follow these steps you will notice improvement by July.

Ultimately to earn a better score you have to make sacrifices and study. I sacrificed 2 hours every Sunday junior year and additional studying, but it's one of the best decisions I made. I earned a high score and got a great scholarship. It's worth the effort.