How long should i prepare??

Yes, that is a good amount of time; in fact, many people who study longer than that simply get burnt out and frustrated. Try to put in 2 hours per day rather than cramming it all in one day per week, and your study will go much more smoothly.

Jim,

You seem like you have an excellent grasp on what it takes to do well on the GMAT. I am currently roughly two months into my studies for the test and I am hovering around the 600 mark on the practice tests. Up to this point I feel I have a decent grasp of the basics, but I tend to get into trouble once I hit the tougher questions. I was wondering what you thought would be the best plan of attack for solving this particular problem? Thanks.

Gabe

It's really tough to say without more specific information. Generally, people in the 600s are good at the basics but still not the best with solving problems. Take the time to analyze every problem you do - including the wrong answer choices - and truly internalize everything. Moving from 600s to 700s is a tough task, and it takes lots of thought. Aim for quality over quantity when studying.