I waste lots of time, doing thinand i keep postponing things which are not of my interest.how can i improve?

Ensure your room and study table do not have many things to distract you. Get a comfortable chair and see that the temperature in the room is not too cold or warm. Tell yourself, after two hours of concentrated study, you shall treat yourself to something nice----a special drink, pie, muffin, etc. Tell yourself that with a total of 20-30 hrs of focused study, you should score 15-20 marks higher in the next exam, for most subjects. Then you will do your parents, teachers, cl-mates(some of them will suddenly respect you!) and principal real proud. Way to go!