Quick tips, in case you are preparing for GMAT. I scored 770 and got a lot of help from friends and forums. Here are things that helped me the most.

Decide a study method – here is mine :

1. Quick glance through materials – Write summary notes
2. Repeat material studied within one week – Review notes and edit
3. Problem solving from various sources – All errors noted, and lesson from error added into the summary.

So by the end of my study period I had review notes along with an error log. The photo of some sentence correction  notes may help. Whatever method you arrive at, please ensure you have summary notes and an error log. On the last day before the exam, going through it will give loads of confidence.

Study Material that helped –

1. Quant – I used Kaplan’s GMAT premier. Also used GMATclub’s Math book – which was very very useful!
2. Verbal – I used Manhattan’s books. The sentence correction book was a blessing.
3. Official Guide – I solved the OG once, marked all my errors and solved the errors again. In certain cases I was wrong again on the second attempt, then I would repeat the process.
4. On the phone – Gmat Toolkit app was my companion for over a month. I solved over 400 questions during this period just during my commute to work. Again, mistakes were reviewed a few times.

Study Timing & Preparing for war:

1. 4 hour sessions on weekends –  A long Reading comprehension passage at the 3.5 hour mark is really hard because you just want the test to end. I think there is just one way to prepare for that – I maximised the numbers of 4 hour study sessions.Important also to not have water/food available (unless during the breaks).
2. Making use of travel time – This was a big win. I practiced sentence correction on my way to work and quant on my way back. ( I enjoyed quant more and could motivate myself on the way back)
3. Really tough problems by the pool side – I used to go sit by the pool side and try the really hard problems. It made the entire drill easier. Also, there was no wifi and phone connections there.
4. Early morning sessions – If you are working then this is your saviour. My goal was to study half hour every morning. I failed sometimes, but sometimes the half hours became slightly longer. Half hours are a simple target and no matter how much you hate it-  just get that half hour done.
5. Practice tests – I didn’t take up as many mock exams as my friends. The exams were useful initially to point out my worry areas and then I continued working at them. I used Manhattan initially – these are harder than the actual test so don’t lose heart. I completed the official test only towards the end of my prep to get a sense of the screen formats.

On the exam day: 

There is plenty of help out there about material you should carry and how you should prepare. Here are my tips, and each of these I tried on my mock exams as well.

1. I carried an energy bar, water and headache pills(just in case). I had already tested this combo on my mock exams – so was good with them during breaks. More energy = more will power. The optional breaks are long enough. Of course, I had arranged my locker for quick access and already tested the bathroom – no surprises 🙂
2. Timing & Scratch paper – It is important to stick to time on the GMAT. The scratch paper was my best friend to make this happen – I adopted a version of the tips mentioned here. 
3. Keep calm and carry on!  – this was the biggest lesson! It is tempting to guess if the question is hard or easy. And when you do that, you get nervous if you are not certain of the answer.  if I wasn’t sure of the answer.  But the GMAT is pretty complex to guess your score. So it is important to accept that you could get answers wrong and still get a good score. So you just need to think of the question on the screen and carry on. When I found my mind wavering, I would rub my palms & eyes to reset my mind , then I would continue one. (my usual technique was to take a sip of water, but I learnt your can’t carry water into the exam)

Good luck!