FarahKhalid
if you are self studying you probably need plenty of recommended books, you must be familiar with different sections in the test, so as the score in each of them, and so on.
as I've read during my research about how to study, and for how long, an average of three months of hard work would be enough.
that's for now, I may come back to continue if you're interested ..

Guys,
I saw the post late. If anyone is still interested, I was a 'self-study' candidate for the GRE. The following resources helped the most.
1. The ETS guide (a must)
2. The 8 Manhattan GRE books. The concepts were explained really well.
3. There are a number of online test resources that are available. Even Manhattan gives you 6 free tests when you buy the books.
4. The ETS PowerPrep software.
That should do.
Regards,
Shouvik.