The first step is always
1. Clone the drive.
But since files are in partitions, you have no choice today on what to do first.
2. Now that we have a clone of the drive we can try the usual titles on the clone.
3. No one usually guesses which method will work. We have tools and apps that work pretty well but more folk forget step 1. Some folk are too new at this and don't know that without a partition we can't have a filesystem and files to recover. Those that are that new to recovery and won't take step 1 should send the drive to http://www.drivesavers.com