TOEFL, AWA I had to take the TOEFL before the GMAT and this helped me overcome some GMAT anxiety because the TOEFL procedure (test center, computer format) is a lot like the GMAT's. I felt quite relaxed before the GMAT because of the TOEFL. Also, reading comprehension on the TOEFL is quite similar to the GMAT's.
I used the AWA as a sort of "warm up" for the real thing ie quantitative and verbal. That doesn't mean I didn't try hard but I tried not to use all my energy on it.
Quantitative This is my weak point so I was surprised by how basic it was. It's actually just about knowing how to find the right solution and calculating as quickly as possible. It was far less complicated than I had expected. I wish I had spent less time on the forum's "hardest questions" part, because they were obviously too hard but had instead done more of the basic exercises. I did not get a high score but I think with this strategy I would have gotten some more points.
Verbal This is my strong point. I have read several times about people getting tired during verbal but I could not believe it when I actually felt like going to sleep right there during the verbal section! I mean this was the GMAT, the real thing!
Grammar and CR were ok, but I have always hated reading comprehension because I found the texts boring and the answers ambiguous. So there I was with these super boring texts and the uncontrollable urge to got to sleep. Of course I lost a lot of time and actually had to rush through the other questions. Avoid losing your concentration by all means, drink coffee before verbal. Try to make the long passages of reading interesting by all means and stay focused. It's the LAST part and you will really regret losing concentration afterwards. My score in verbal was quite good so it's sad to know that I could have done even better..
Other I found the staff helpful and friendly, the digital signature, fingerprints, photo shots, being filmed during the test etc. were neither complicated nor scary.
The pauses were not long, but long enough to use the bathroom, eat and drink and put my head out of the window to breathe fresh air. You don't have enough time to worry during them, probably a good thing..
Take a GMAT practice before to get used to the format! I didn't and I regret it deeply now.
There were many students with me in the same room during the TOEFL. It tends to get quite loud but I found it reassuring to be surrounded by other students. I was the only one at the GMAT which was quite nice. Staff are relaxed and friendly, it's easy to concentrate.
It's been said before, try to visit the test center before the test. It that's not possible, no problem, but arrive early by all means. Even if it's just to stand around before the building to drink coffee. Believe me, I speak from experience..