Costing is a pain

 HI All,

i am am Pe student who just failed in group 2 for the 3rd time ... i am just not willing to give up no matter wat . i always manage to clear in income tax & Infotec ... i am not so sur as to how to prepare for costing. importance to theroy or practicals are better way  to score...... how do i prepare

please help any suggestion of books also will be valuable ..........

Thanks

VJ