Your GMAT advantage

Most business school applicants are generally quantitative so their math scores are usually quite high. It's a wash. Thus, for you the applicant, I recommend really honing in on the verbal section to inflate your score. To do this, I would recommend reading the grammar books.

I know it doesn't sound exciting, but for those sentence questions, they are your only hope.

Thus when you take practice exams, see what grammar rules you keep messing up on, match them to the grammatical concept, and drill yourself on it.