Every time a student thinks of how to prepare for GRE and there are lot of means he/she can go with it. Some may refer to Online GRE Prep, coaching or a mix of Online GRE Prep & coaching, or one on one Online GRE Prep, however if you look at the source preferred by wide majority of students who aspire for a high GRE score would be Online GRE Preparation.
If you look at the reasons for this preference of Online coaching among students,
(1) The GRE math practice test require you to be more fluent in using the virtual calculator during the exam. In fact in comparison to a student who uses GRE Study Guides or books and Online GRE Prep, the latter are quicker than former by 6 seconds/questions. This 6 seconds/questions can play a significant role in your GRE Quant
(2) As the GRE exam itself is Online, it is highly recommended to use Online GRE Prep as it will give you the actual experience of the GRE compared to any other form of learning.
Now to address the question best materials, there are hundreds & hundreds of GRE books, GRE Study guide available both Online & offline. It would not be possible for a student to cover all the materials. Added to that, each book would be recommended for different concepts. The smarter thing a student can do would be to first identify his/her own stronger and weaker areas with respect to GRE & decide the materials needed accordingly which is easily possible in Online GRE Prep. For example, very few Online GRE Prep portals like the GREedge Diagnostic test can help you identify this. Post that, they also provide detailed feedback on your performance. Once you have this feedback, you can find materials that can build your fundamentals only in your weaker areas rather than going through the 100s of books available in the market. Now the question is how can someone handpick these concepts for your weaker area and give it to you right? This is where Online GRE preparation forums have a significant advantage.
And personally I feel, among the Online GRE Prep portals GREedge goes an extra mile by providing an online trainer who provides feedbacks that are so personalized using the constant reports on your progress and preparation generated using technology. I think they can provide you the best study materials that are personalized for a HIGH Score. You can visit them at www.greedge.com to know more. Hope you have got a right idea on How to prepare for GRE.