your question is quite foolish. i mean you can ask that how to get my self good in essay writing instead of how to get 70+ marks in essay . well if you really want to get high scores in this paper then you should work on your english grammar , vocabulary , writing expressions ,idioms etc .. make good and proper notes of different topics having important dates , facts , figures , statements etc related to each topic . get checked you essays on regular basis by any english teacher. you know practice makes man perfect. so keep on practicing . and do not prepare to get 70+ marks , try to get 100 marks in each paper . why you make your aim so low ? trust on your self and test your limits . May Allah bless you.

Regards