How to improve?

sunilrawat wrote:Hi,
I have been preparing for GMAT for the past 4 months. I started from a score of 550(GMAT prep 1)
I studied from the following:
- OG 12
- Manhattan SC
- BTG forum
Subsequently my score improved as 600(GMAT prep 1 repeat),610(Veritas prep), 660(Mastergmat) and 680(Grockit).
But as my exam date is approaching, my score has fallen down.
I scored 600(MGMAT) and then 550(Knewton). Instead of improving further, my score is worsening even more. How do get through it?
My exam is due on October 10. I am scared.
Please help.

You are comparing apples to automobiles. It makes absolutely no sense to compare scores between different test sources - each source has its own bias and inner score calibration. The reason to do simulation tests is not to see what your score is, but to practice better time management and remaining focused for long period of time under test conditions. If you want to really improve, take several tests from the same source, presumably using the same algorithm and questions source, so that the results can actually be compared to each other and you can actually try to make some sort of attempt to do things differently and improve from one test to the next.