You mentioned that in your last attempt, your timing was off...so perhaps if there is not a particular academic area in which you feel you should improve, you should focus on your test taking skills.
You will have about two minutes to answer each question on the Quant section, and slightly less than two minutes per question on the Verbal.
A tactic you can employ to develop your time management skills is to group five Quant questions together and spend no more more than ten minutes on them. For Verbal, give yourself nine minutes to answer five questions. You can use this strategy on both practice questions and simulation exams.
If during a ten minute stretch, you find yourself falling behind schedule, make a strategic guess or two to catch up. Make strategic guesses on questions about which you aren’t confident or that would take you much longer than two minutes to answer. By making strategic guesses, you can recover precious time that you can spend on questions on which you have a better chance of answering correctly.
To sum up the basics of time management on the GMAT: keep track of your time, and if you start to fall behind, make an educated guess or two to ensure that you will not run out of time and leave questions unanswered.
Economist GMAT Tutor