Before starting recovery make sure that you have a good cold or hot backup and all the required archived redo log files
and of course your database must be in archivedlog mode.
follow these steps.
1. shutdown abort
2. Rename the corrupted datafile or copy it to some other directory using OS command.
3. Restore the datafile from your backup to the original location.
4. startup mount
5. recover datafile 'file_name'
6. apply the archived redo logs
7. alter database open
8 don't forget to take a cold backup after finishing recovery