well.. heres my basic layout.. i got 12/20 which is alright for me in an essay would have gotten better mark but ran outta time.
well.. naturally the first paragraph or two should have info on his early life/ life before his trip to the USA... mention where he was born.. what he did.. his wrtings that sort of thing, a useful thing to add would be the range of his publications.
in subsequent paragraphs talk about 1 basic point at a time.
make sure you mention BOTH the positve and the negative implications/ the intended use of the three concepts, aquida jahilliya and jihad which were advocated and modified slightly by Qutb to be more relevant to modern society... when in assessing or evaluating you have to make a judgement so you must therefore try to look at both sides of the arguement (for example you cant just talk about the outright negative impact of qutbs writings aka terrorism.)
another extremely important thing you need to mention is his three prominant publications 'social justice in islam 1948' 'milestones' and the multivolumed publication 'in the shade of the quran/koran
and remember since the question askes you to judge the contribution in both negative and positive forms. you therefore need a conclusion in order to sum up what your judjement is