I'd recommend a review course such as GT or School of PE. I think both are good. The Graffeo book is an excellent resource for the exam. There is some good information inside and I would tab all of the tables, charts, etc. Work EVERY PROBLEM in that book including the examples and the practice tests in the back. The Graffeo book doesn't do any amount of training for the NEC/NESC but grab a book and the NCEES practice exam to get an idea along with the Complex Imaginary code book and practice exams. I went through the entire graffeo book including the practice exams before the 6 week online course started and that was a big help. The online course moves fast and there is homework issued. I would have been lost if I hadn't already put in lots of time studying.
About calculators....
I brought two to the exam, an HP35s (primary) and a Casio fx-115ES (backup) along with a new set of spare batteries. I used an HP scientific through my engineering courses at Uni (HP33S) so I had a lot of exposure to doing calculations with my HP. The best thing about the HP35S is that it has a robust algebraic solver and the ability to store formulas. This is great for doing relatively straightforward calculations that can be error prone (like calculating the +, - and zero sequence currents). One of the best features of the Casio fx-115ES is the excellent complex number menu it has that allows for rapid conversions between rectangular and polar formats. You can even enter polar and rectangular numbers as part of a calculation (and the display looks exactly like what you have on your paper) which is sweet.
The best advice I can give on exam day is bring your own lunch (don't leave the test location property) and don't get flustered. Keep calm, cool and collected. The minute you start thinking you've lost the battle close your eyes, look at the pretty woman across the room, think of how that beer will taste later tonight when you're out of the exam. Find something to escape to for 10 seconds then open your eyes, re-read that problem slowly and attack it. No amount of studying for this test will help more than the ability to not give up and to keep going when you first read that problem and panic because you have no clue how to solve it.