I took the GMAT FE for the second time and scored a 745, which I was thrilled with. I studied on/off for nearly a year (but really buckled down for the last few months before the test) and ended up taking the test on the last possible day I could for the 2+2 application, which I would not recommend as that deadline definitely caused unneeded stress. I've always been a fairly good timed-test taker, mostly because I work quickly. However, preparing for the GMAT FE was much more difficult than I anticipated, because it's a test that demands accuracy, and I tend to work quickly but not very accurately. Shoutout to TTP for helping me improve my accuracy and build confidence working through practice problems and learning tips/tricks for checking accuracy.
Biggest thing for me was taking practice problems, zeroing in on the questions/topics I missed consistently, and drilling those over and over and over again, until I couldn't miss them. Also, practicing with a whiteboard, in the same room I planned to take the test in, made a big difference.
Even with lots of practice, I still feel like the GMAT FE involves a lot of luck, because the amount of questions is so little and each one counts for so much. I took the test twice, about a month apart from each other, and improved from a 655 to a 745. Some of that was a lot of drilling quant problems (which was always my weakest area), but some of it is simply due to getting a version of the test I liked more and performing better on test day.
I also would recommend taking the test day itself seriously--the second time I took the test, I got better sleep before, exercised that morning, and drank lots of water leading up to the test, and I feel like it made a difference in how well I was able to focus. Also, the first time I took the test, I studied hard the day before. The second time, I gave myself a break for a couple of days leading up to the test, and that break gave me a boost in my ability to reason quickly on test day.