For business, I'm sure your teacher would've advised you this already but it cannot be stated enough - knowing your syllabus. Given the structure of most responses, like explain or justify or assess, definitions to supplement each topic in the syllabus is vital for good answers. Then again, with elaborating on said definitions, that is dependent on your understanding of terminology and concepts but it's a minor segment of your responses. One other good tip for writing responses in businesses is how many longer responses almost suggest you to relate your given strategy or process to an overarching goal or role of the business function. To summarise, syllabus, definitions and link to goal/role of the business. Additionally, statistics and a comprehensive knowledge of case studies is truly beneficial to essay writing.
For legal studies, multi choice is just a matter of doing them over and over again to increase your exposure to trickier questions and improve your application of various parts of crime and human rights in different scenarios. Practicing short answer and essays to old papers and more importantly, mixing it up with making your own questions, is pretty helpful. You can make your own questions by choosing a random verb, a theme/challenge from anywhere in the syllabus, and a random topic from the syllabus. This should prepare you for a multitude of possible essays, and the choice of questions with this method is immense.