Step 1: Plug in the jump drive and open Disk Utility.app. (/Applications/Utilities/Disk Utility.app)
Step 2: Select the jump drive in the sources column on the left. (Do not select the indented portion.)

Step 3: From the top half of the window, select "Partition".

Step 4: Change "Volume Scheme" to your desired number of partitions.

Step 5: Enter in a name for your partition(s).

Step 6: Change "Format" of each partition to "MS-DOS (FAT)".

Step 7: Click on the "Options…" button under the partition arrangement section.

Step 8: Select "Master Boot Record" from the window that appears.

Step 9: Click the "Apply" button and confirm your new partitions. (If you get an error saying that the disk cannot be ejected, eject the disk in Finder then reinsert it.)