Actually, you can’t! This is what one of the developers, Andreas Dilger, said about it:
“In order to ensure that ext3 can safely resume an unlink after a crash, it actually zeros out the block pointers in the inode, whereas ext2 just marks these blocks as unused in the block bitmaps and marks the inode as “deleted” and leaves the block pointers alone.
Your only hope is to “grep” for parts of your files that have been deleted and hope for the best.”
This is pure hogwash. Why create a filesystem that if I accidentally delete something, that would be the end of it? One man,or hero in the name of Carlo Wood , who also thinks along the same lines as myself (though I lack the knowledge he has), thought this was unacceptable. So he set to work. And “three weeks and nearly 5000 lines of code later,” he created a cool way of recovering your accidentally deleted files on Ext3. You can join his project site here.
I also do encourage you to donate if you can to support this nascent app to become mainstream in the future. So if you have ever landed yourself in the misfortune of having to recover files on Ext3 that you accidentally deleted, Carlo Wood is your man. Pay him a visit and tell him I said hi.