Scoring poorly on your first GMAT attempt is not an uncommon experience. Please do not dwell on how poorly you performed but focus on how can you do better and where the problem areas of the exam are. I recommend that you do another diagnostic exam and see those areas where you excel and those areas where you do not - and really focus on those areas where you do not excel at. In short, it is the problematic areas of the exam that are going to keep your score down.
Also, I recommend that you hire a tutor to assist you with the areas that are posing problems. Even if you sign up for a class, being with so many other people in the class will not give you the chance to dig down deep enough to really address the problem. If you are able to really identify what your problem areas are - and then properly tell your tutor what these are - and keep your tutor focused on these issues -- then it is a worthwhile investment to make and I am sure that your score will increase significantly.
Good luck and stay positive.
Kimberly Plaga
Senior Admissions Consultant
Manhattan Review