You cannot only get good grades by studying hard, you also need to do several important things. First of all, you need to participate in the classroom and finish your home work. For example, participation can show you have a great attitude towards learning. Doing home work is like a self-check when you make a mistake, so you practice with home work to make sure you remember it correctly. Next tip is to be active in the classroom/class and help other students, because while you're learning a language you should use it all the time. Otherwise, you would not be practicing, for example your English skills. 

You need to try your best to get points over 70% in every test, because it is added to the final grade. In addition, if there are thing you do not understand, you can just ask for help, you can ask your teacher or your classmates, I believe there are many people who would like to help you. For example, you can ask your teacher after class or send an email to him/her, and ask your classmates and offer to pay them with a pizza, in return for their help. 

At last, in order to have good grades you need to be healthy physically and mentally. When I relax and get sufficient sleep I always do well in my exam. 

 All in all, these are good ways of how to get good grades.