If you need to learn grammar and syntax, the best way is to practice by diagramming sentences and making sure that you know exactly what the different parts of speech are. This kind of studying is best done cumulatively and not left until the last minute. Reading a process essay about how to study for an exam is not as helpful as a short amount of daily studying.
Doing worksheets about English grammar and syntax are a great way to learn the rules of grammar. Also, reading books is another excellent way to learn what each bit of punctuation does and why it is important. The more you read, the better you’ll know English.