- Shut down the machine if you didn't already,
- boot a Live CD like KNOPPIX or HELIX (or use your other GNU/Linux installation as long as it doesn't alter the "victim" partitions), and
- attach storage (internal harddisk, external USB drive),
- mount it, create and format a partition if necessary, then
- make a 'dd' copy of the "victim" drive to a file on attached storage for backup purposes.
- mount the partition containing the dd image and
- one partition for recovering files to (don't use your "victim" partition),
- run Photorec, select the dd image as source and configure the destination,
- select document types to recover then let it do its magic.
Your chances of recovery roughly depend on
- file system state (clean vs dirty, corruption),
- the time that lapsed between deletion and detecting deletion (as in writes to the disk),
- the Photorec version (latest is better),
- file type to recover.
Manual pages you'll be reading before performing tasks: fdisk, dd, photorec. If you've got any questions after reading those (and preferably before executing commands) let us know.