Hi,
Having had this experience of retaking the GMAT, I know and can truly vouch for the fact that going through the exam material and attempting practice tests is real and rigorous.
But one thing that I observed was that it is the weak areas that make one panic on the exam day. I remember I did very poorly on my first GMAT and later after the exam, when I sat down to introspect, I could not even do good on those sections that I was good at and confident about.
So, the first and foremost strategy that exam-retakers need to formulate is to figure out their weak and strong areas.
Once you do this, all the following strategies should be aligned in a way that you make your strong areas much stronger and work upon your weaknesses until they don't seem like a weakness that affects a deterrent to your exam day performance. Rest strategies keep on unfolding as you practice on the way.
Practice, Strategize, Excel...
Hope it helps!