A preface, I took the GRE before and scored a low score of 280. I was very disappointed until someone told me to use Kaplan.
I would highly suggest signing up for Kaplan before you take the GRE test. It goes through every section and has quizzes to make sure you understand the material before moving on.
One feature I used sooooo much and helped out with my quant was the Qbank! I started off with low problems to get some confidence and then onto medium and hard. When you get a questions wrong they have a full blown explanation on how to do the problem so you learn from your mistakes.
I highly recommend Kaplan! Great service and really helped me improve my score to get into school!