Step-by-step explanation:
1. Breathe. While grades are important, they do not dictate your future.
2. That depends on if you're studying is about really learning the material, or just cramming for an exam.
3. If you're studying to learn the material, then repeat it over and over until it becomes second nature. I'm not saying study endlessly, but dedicate like 40 minutes to studying one subject. Go online and find how others solved similar problems.
4. If you're studying to cram for an exam, then study outloud. I find that when you think in your head, you don't hold on to the facts as well. When cramming, try talking outloud, have a discussion with your friends and peers about the material. Group thinking is great.
And for just studying at home, write it down. You tend to hold on to information more when you wrtie about it extensivly.