I have tried all of the above, and i dare to say that eah methode worked out ina different subject. First, scientific subjects, u need to memorise or have a backgroundabout the theory, then apply it to exercises, because solving the problem depends on the situation and the iformation given, if there is anything like graphs or reactions or anyting of the srt u need to visualize or sketch ona peice of paper, dun give up easily coz it feels really good when find the answer. Secondly, as for Litterature subjects, u may need to memoize an also understand the texts given to u, it's more likely u'll be asked ur opinion of the mater discssed, so when u read try to form ur own opinion, consider all the concrete and abstract aspects of the subject, if ur reading a novel, don't just think of what's going to happen after, study carefully the charecters, the ambiance, the realtionsof the events, if it's history follow up the events and see the impacts of the decisions or wars for example and the evolution of the country, again for exapmle. As a final point. u need to understand everyhing ur doing or asked to do when ur studying, whether it's scientific subjects or litterature ones, u need to analyze, and conclude. Good luck in ur studies.