Hi Anthonydh,
Thinking about the GMAT this far in advance of when you'll actually take it is a remarkably proactive choice on your part! Based on your post history, you were clearly studying for the GMAT at various points over the last couple of years, so I assume that your application plans changed. Beyond thinking in terms of how you can be more prepared for your GMAT studies once you (re)start them, you might also think in terms about what you can work on to make your OVERALL application profile stronger. If you have an idea of the Schools that you want to apply to in the future, then you would likely find it beneficial to speak with an Admissions Expert about your overall profile and plans. Those Experts should be able to help define the specific areas of your profile that could use some improvement.
There's a Forum full of those Experts here:
https://gmatclub.com/forum/ask-admissio ... tants-124/As far as general GMAT skills are concerned, the ability to quickly (and correctly) work through Arithmetic and Algebra by hand would help in the Quant section (even though the Quant section is NOT a 'math test', you'll still end up doing lots of little calculations as you work through it). Having all of the necessary math formulas memorized, as well as some broader math knowledge (fraction-to-decimal conversions, prime numbers, etc.) would also help you to work through the Quant section more efficiently. For the Verbal, you could work on your standard grammar knowledge and GMAT idioms and train to hone your 'active reading' skills.
GMAT assassins aren't born, they're made,
Rich