Hey Souma,
Here's four major tips I'd recommend for your Round 2 prep:
1. Diversify your materials. How did you study on the first go-round? Make sure you are using books like the OG, MGMAT, Powerscore, and other hard copy study guides and online resources. Studying online with Grockit, Beat the GMAT, and other sites is vital to building your comfort level with the computer-based format of the GMAT as well. Be honest with yourself: were you using the Best of the Best?
2. Study less more often. When do you study? Do you keep a regular study schedule? Or are you studying intermittently in long blocks that ultimately wear you down? Make sure to keep a strict schedule and abide by it, even if you'd like to squeeze in a few hours. Staying up all night to cram in yet another practice test is not always the best choice. Study in smaller bursts, take frequent mini-breaks, and give yourself simply accomplishable tasks.
3. Find your community. In addition to the friends you make on Beat the GMAT, seek out a local in-person GMAT study group. Set goals with each other, and see what advice they have. If you have a 600 and are eyeing a 700+ score, there are many people out there who have made that leap. Success leaves footprints. Find out what strategies are commonly used by 750+ students, what study plans they keep, and how they build their content-knowledge.
4. Review your old materials. Re-take quizzes and practice tests from the very beginning of your GMAT studies. Do you find yourself getting the same questions correct. This can be a sign that you haven't learned the content you think you have. Be honest with yourself about what is "sinking in" and what is not. Are there gaps in your math or grammar knowledge that still need to be filled? Are you rushing through your practice questions, and not taking enough time to review incorrect answers? Consider making an error log to help you discipline yourself and use the 40/60 rule. 40% of your time should be spent actually answering questions. At minimum, 60% of your time should be spent reviewing.
Hope this helps! Feel free to email me if you have more specific questions.
Best,
Vivian