Mahrukh, I think you should visit "Just finished my GRE" section and get an idea what did others do to prepare for the exams. these are the ones who have given GRE, so try to get some sort of input from there that what did they use to study and what did they find more helpful to prepare for the exam e.g which Book? which preparation course? what ere their strategies or plans of action. There, others give their comments and ask the test-taker to tell his specifics regarding test and many other questions, so all I can say is after visiting that section you'll have an idea where to start from as you have a picture in mind how others started and then finished it successfully with nice scores.
And yea, start from Vocabulory and get Bigbook for practice (to be used after you know what GRE is and get overview of topics used in GRE), for Math I believe Barron's and Nova GRE Math Bible are nice ones and for vocabulory again Barron's and also get some Flashcards (Kaplan flashcards), Kaplan GRE verbal book has "GRE Word Groups" and GRE root words and also nice tactics to solve questions but first learn Vocabulor and Math content (topics like Arithmatic,Algebra,Geometry,Word Problems, Graphs & Charts for Data Interpretation), and also Reading Comprehension (read The Economist or/and New York Times, or editorials Wall Street Journal or/and any other useful resource) as far as RC is concerned do learn how to read fast but with understanding (there are some strategies but need practice). for Analogies you need good vocabulary as well as know the relationship between words (well explained in Barron's and Kaplan verbal book).
But first start from Vocabulary (maybe 30 to 40 words per day or as much as you can, try to make your own sentences and maybe make flashcards and record your sentences using Anki software) and at the same time review and do Math exercises on daily basis and then at weekend try Practice Tests from BigBook.
Hope this helps!
cheers