Math, science history- practice the questions. English is trickier because it asks you to write 4 essays. Although you should certainly look over the test to get an idea of what it’s like, the only way to really prepare for it is by writing essays! Also, read a lot, because one of the essays will ask you to relate 2 books to a statement. The more you read, the easier it will be to think of 2 books that relate.
Also, visit regentsprep.org for more tips and old tests.