well…letmme tell u dis first…”there is no substitute for hardwork..”..so it simply means u hav to work very hard…start your preparations atleast a month before..write out a schedule..also wen u study, keep an hour for each subject..ie after each hour change de subject…it keeps ur mind fresh ..it always works for me..moreover donot keep ur hard subjects for the last min..subjects lyk maths have to ritten down an practiced…moreover the tym u need also depends on thewich class u r in…also be sure to keep the last week for revision..!!moreover being more specific abt wen ur xam is would hav helped to giv more relevant answers..