Anxious business-school applicants have something to add to their to-do list: preparation for the new "integrated reasoning" section of the GMAT.

Although the new section was initially announced a year and a half ago, the Graduate Management Admission Council has offered scant details about what questions will look like and how they will be scored. With registration for the new test starting this month, many students are wringing their hands. Some test-prep experts say they may even see a rush of applicants wanting to take...