hi priya ,
if u r really planning to take GRE , then i would suggest u to go thro barron`s word list for vocabulary , i feel its the best and if u can master this , then u can tackle the verbal section well.
there r many books like princeton, arco , kaplan.
u can also practice with CDs , which will give an actual idea of the exams .
u might need 3 - 4 months for preparing.
but as griffin told, all the MS progmm dont ask for GRE .