Is flashcards useful in GRE preparation

Hai … i am in a plan to prepare for gre …is the flash cards usefull in preparation…is it alone enough for preparation …since i dont know how far it covers gre…

if anybody having used flashcards …i am ready to buy
mail me if so

which is the right month to take gre if i plan to join in 2008 …what other books should i read other than barrons

Thanks in advance