Retake the GMAT if your school allows it. Some business school programs will consider two sets of scores in the admissions process. Check with your intended program's admissions office for their application guidelines with regards for sending in more than one GMAT score.
Take higher-level math courses to compensate for a low GMAT quantitative score. Class credit in statistics or calculus courses will inform the admissions board of your knowledge of quantitative problem-solving.
Take higher-level writing or speech courses to compensate for a low GMAT verbal score. Credit in classes that particularly deal with reading comprehension and expressive skills may overcome a low verbal score in the eyes of the admissions board.
Get experience in the business world. An internship or summer job may give you the additional boost you need for program admission. Experience at a corporation or office will also expand your network of contacts in the business world and give you possible personal references to include on your application.
Have more than the required number of personal recommendations. Extra personal recommendation letters included with your application will impress the admissions board, especially if your references are alumni of the program or people in the industry.
Write a spectacular admissions essay. Look at example essays for inspiration. Bloomberg Businessweek (businessweek.com) has a few example business school application essays available on their website.
Explain your low GMAT score in your essay, but don't veer too far from your original topic.
Triple-check your admissions essay for grammatical or stylistic errors. Have it proofread by someone else. Also check your application forms for any errors or omissions.