Having ownership over material you're getting right (ie. getting it right because you know it, not because you sort-of know it or because you guessed) is KEY to continuing to get questions right.
Understanding why you got something wrong, why you were sidetracked/seduced into the wrong answer/fell for decoy is also important. Many of the answer choices provided on the test are there because many people before you thought they were right (erronously), or the numbers (in the case of math) are within the computation of the question, itself.
Always RE-READ the question to make sure you've answered what it asks, rather than providing an 'answer.'
Another great practice is to understand WHY the other answers don't work, in math and verbal (it's often more obvious in verbal).
Each question you do, once you complete the diagnostic or finish 'correcting' your homework, should be a dialogue so you can turn the doing into owning...a very different relationship to questions.
The more real questions you work with, the more you'll get a sense of the predictable ways the GMAC creates answers.
This is an incredibly important part of the process and if done correctly, will ultimately make a big difference in your score.