GRE Preparation can take between 2-4 months depending upon your aptitude. It also depends upon the time you have at hand, the schedule of your university examinations , college examinations, and your other commitments.
The best part about the GRE is that you can postpone your examination date even two days prior to your allotted date.Therefore if you are not scoring well simply postpone your examination !! No, this is not a loser's option ... infect it is a prudent decision that could ENSURE YOUR SUCCESS . The simple fact is that it is impossible for your score to increase substantially in the last ten days before your examination date. So only if you are ready to accept your average score on your practice tests should you proceed with taking your main test.
The ideal time for engineering students to start their preparation is immediately after their fifth semester examinations. Choose an examination date in the first two weeks of April.If you are not prepared by then, postpone your examination date to August/September.
Students from the first year of engineering should not bother about GRE. Get all your fundas right this year and no KTs and rest of engineering should be a piece of cake !
Likewise students from the second year should devote more time on their acads but can start off with their Verbal preparation and hey...relax...this is probably the only year you can really freak out....