need edexcel exam help...

[Shah...]

salam, i am going to give my edexcel AS and A2 bio and chem exam this june, ie june 2013...those of u who already have given the AS and A2 exam in my subjects..plz help me out,,how should i go about revising..am very scared for unit 4 and 5 for both the subjects..any good tips..i already have the edexcel revision guides for AS and A2 for both subjects..(also give ur grades with the way u studied)..
THANX IN ADVANCE...