I took my GMAT for the first time and scored 500 and on my second attempt scored 610
So its just hard work , practise and determination to do it. Just study what are u getting wrong and why. Make notes of it and regularly participate in the forum.
Dont re-take it in a haste . Take the exam only when your confident and consistent in your practise score. I just used Kaplan and Princeton Review plus TEST MAGIC which rocks !