When it comes to assignments, as the others have said, try to start them as soon as you can. You don't want to be stressed out by leaving them to the last minute. It's better to do it over time than to do all of it on the last day, because you'll have more time to find better ways to approach the assignment and maximise your marks.
For exams, studying depends on the subject. In English, you want to be writing practice essays, integrating important quotes in both an open and then closed book environment. For Maths, you want to be doing as many practice papers as possible while trying to understand the concepts that the question assesses. And for say, Chemistry, you want to be learning all of the content by dot point form and then doing practice questions both with and without your notes. But as you can see, for most subjects, it is important to apply the material. That way, you'll be familiar with the style of exam questions and you'll be more precise and accurate with your answers to the different types of questions in the exam. You simply can't just memorise your notes and expect high marks (although this works for some people) - memorising doesn't result in an ability to solve problems. Applying the content is the best way to study for any exam.