Most of you probably know this already but I want to reiterate something that could help those who just started studying.
My tip is not rely just on paper exams. That CAT practice such as questions on
Magoosh is a must.
So I started my GMAT. I took the real GMAT and got a 620. Without studying.
My math score was 50 percentile. My SAT math was 99% so I was really shocked. So I decided to do all the OG questions. I learned a lot and I tried to solve all the questions. I studied this for perhaps 2 weeks. I was getting confident so I decided to take a practice CAT. With the GMAT official exam. (Noob mistake. I should have saved). When I took the exam, I was compeletely in shock because I was not used to the CAT. I was only used to the paper so I started to panick.. I didn't have enough time to finish either because I didn't practice the timing for the questions either..
TLDR. Mix up paper questions with CAT questions as you study. The different formats might shocks you.