There are things you can do to try to minimize careless errors - is that what you're talking about? Read this:
http://www.manhattangmat.com/blog/index ... -the-gmat/You'll always have some incorrect answers, though, because the test can just keep giving you harder stuff... so you'll never completely get rid of all incorrect answers. This is different than minimizing careless errors. :)
For MGMAT, we require a score of 760+, as well as significant classroom teaching experience. (And I want to mention that the second item is the harder one to pass during the audition process. Everybody we reject, by definition, has a 760+, because we won't even audition you if you don't have the score. And yet we still reject 90+% of the people who do have the score. Also, once you are in the 760+ range, we don't care if it's 760 or 800. At that point, all that matters = your teaching skills.)
So, yes, you do need the score if you want to teach for us. You also need to be a very good teacher - which is a different set of skills. :) Our standards are the highest in the industry; you won't need 760+ to teach for other companies. (Not trying to market anything or brag - it's just a fact that nobody else has this requirement!)
Good luck!