I took the GMAT twice and through my study period I had a little notebook that I jotted down all the important points in.
I vowed that I would put them online for others to use them and I just finished doing that at last. I still have more advice and tips to add but my fingers are tired of typing and Word isn't very equation friendly (you have to go select each equation template from a different selection then fill in the blanks..) As for now, good luck to those planning to take the GMAT. It's a tough exam so study hard and spend a few days surfing the web for advice because there are many free guides online, and they are really helpful (do that only if you have more than ten days left before your exam date!)

Here are the tips I compiled for you: https://anamethyst.blocked/