What are the good ways for studying so you can do well in exams?

Hello people . (: I am a 14 year old girl . This year is a crucial year for me as we're going to be put into classes with different combinations like Triple Sciences ( Bio , Chem and Physics class ) , Biochem class all these which decides my future occupation already . ): And till mid year exam , my results are like crap . My mum cried . )': I dont want to see her like that and disappoint her again because she led a miserable life since young. i really want to have an achievement for her and myself . :/ Im very hardworking now like everyday go school , come home, eat study all the way and sleep . And its a routine but I'm still not very sure of my studying method because it doesn't help in my exams everytime . ): So , any kind souls out there are willing to share with me how you guys achieve good results? I need it very urgently . ): Thank you , love you guys . ): <3