I think that the Kaplan tests are excellent for the math sections, but not exactly on target for the verbal sections. The easiest way to get an incredible score is to be sure that your sentence correction skills are very top-notch and to practice every math question you can. On the test, if you guess one question, be sure not to guess the next question, as your grade will probably swoop down.
ETS does sell 3 tests, and a while ago they sold batches of 3 tests. I wonder why they stopped.
Try to find an old edition of the 7th edition of
the official guide. There are hard questions there that have been left out of the 10th edition.
Another note: As there may be TOEFL test-takers taking the test at the same time you are taking the GMAT, study with background noise at least part of the time. Also, try to learn how to work with earplugs, because if you have a noisy atmosphere and complain, you will get a pair of plastic earplugs. Not comfortable, and they don't eliminate much noise.
Good luck.
Leanna