Formatting a hard drive on a OSX computer is just a simple as a Windows Machine.  Naturally, Apple has to rename all of their hardware tools but they all basically do the same thing.  In OSX Lion, you find ‘Disk Utility’ under the “Other” menu when you press F4.  From there, you simply select the drive you want to format and click on the “erase” tab.  From there you can wipe out the hard drive.  There are lots of other neat tricks you can do here such as setting up custom partitions that work on both Mac and Windows PCs with no 4gb file size limitation.

The key is to alway back up your data and make sure that the backups do not live on the same drive you are formatting.  Deleted Mac files are harder to recover than their windows counterparts.