You have to have at least one partition on a disk to make it usable. Click on the Partition tab in Disk Utility. Near the bottom you should see a button labeled Options. Click that and choose GUID.
Save that setting and Type in a name for the new disk. Choose Mac OS Extended (Journaled) as the Format and click Apply (Warning: This will erase any data on the drive.)
If you want more than one Partition on the drive, (each partition will appear as a separate drive to the OS) change the volume scheme to your desired setup.