Create your own organization
If you have ever seen your classmates notebook you should have notice that everyone has a different way to take notes. Mine is using bright colors in the titles with big letters on the top of the page, in this way at study time it is easily to find the subject, also writing the things that appear on the board in blue and the explanation that the teacher gives in black.

Explain to somebody
Tbh, i have noticed that when i explain the subject (and also argue about it) with my friends before a test helps me to remember and understand much better, because in that way you can speak about it with someone that has your own vocabulary and same knowledge.

If you have a doubt ask your teacher or get help with some classmate, there´s always someone disposed to help.

Pls don´t disturb
You can not pretend to have good grades at a subject if you are messing all around the class and doing nothing (admit it at least once in our life we all have made this) , it´s also unfair to your classmates that are trying to pay attention.

Project yourself
Just think about it, some 40 minutes of studying math today can mean good exercises tomorrow...those can help you to get good grades at school...or university tomorrow.Just think about those times that you have fuc**d up something and after that you were wondering "what if i just...?"(This also works pretty well at every day decisions)

Pd: Si hablas español... Holi :)