Make sure you understand each topic/concept when you first learn it (this is recommended for all science courses). Don't wait until the day(s) before to review because you can't really review things you haven't learn or understand already
During class or after, ask questions to make sure you understand the concepts. Double check your understanding on the homework. If you don't understand, you must seek help right away
As an option, you can watch the lessons on my Youtube channel and take notes. Students in the past found relearning the lesson again very helpful.
Practice/review all questions in the HW, quiz, PowerPoint, Kahoot and class packet (easily 300 to 500 questions). Make sure you understand the reasoning behind each answer. If you don't understand why that is the answer, you must ask for help and not just hope you wont see it on the exam.
These questions are often repeated on exam and it is disappointing to get questions wrong that was covered during class or homework. If you get questions wrong on homework and quiz, make sure you understand the right answer.
Also I tend to select recent questions on the recent chemistry regent exam(s) to be on the exam
Students in the past have taken pictures of questions that they have difficulties with and then used the remind app or email to message me to ask why and how to do the question.
Ask for help after class during a free period or afterschool. Ask first and don't just show up.