Automatically mount a 2nd hard drive in Debian 7?

You'll need to manually make a mountpoint and add it to your fstab file. As a step-by-step:

1. Create a directory to act as a mount point: sudo mkdir /media/mymountpoint
2. Get the hard drive information (UUID is best, since the dev name can change) sudo blkid (thanks @ernie, I mixed them up) [Find your drive and copy the UUID]
3. Unmount the drive sudo umount /dev/sdX#
4. Edit your fstab file sudo vim /etc/fstab
   • You need to use the layout (on its own line) UUID MountPoint FSType Options Dump Fsck
   • As an example, here is mine for my Windows side
   • UUID=MyUUID /media/windows ntfs-3g defaults 0 0
5. To avoid rebooting, you can do sudo mount -a (mount all).

From man fstab:

The first field (fs_spec).
          This field describes the block special device or remote filesystem to be mounted.
The second field (fs_file).
          This  field  describes  the  mount  point for the filesystem.  For swap partitions, this field should be
          specified as `none'. If the name of the mount point contains spaces these can be escaped as `\040'.
The third field (fs_vfstype).
          This field describes the type of the filesystem.  Linux supports lots of filesystem types, such as adfs,
          affs,  autofs,  coda,  coherent, cramfs, devpts, efs, ext2, ext3, hfs, hpfs, iso9660, jfs, minix, msdos,
          ncpfs, nfs, ntfs, proc, qnx4, reiserfs, romfs, smbfs, sysv, tmpfs, udf, ufs, umsdos, vfat,  xenix,  xfs,
          and possibly others. For more details, see mount(8).
The fourth field (fs_mntops).
          This field describes the mount options associated with the filesystem.

          It  is  formatted as a comma separated list of options.  It contains at least the type of mount plus any
          additional options appropriate to the filesystem type. For documentation on the available mount options,
          see mount(8).  For documentation on the available swap options, see swapon(8).
The fifth field (fs_freq).
          This  field  is used for these filesystems by the dump(8) command to determine which filesystems need to
          be dumped.  If the fifth field is not present, a value of zero is returned and dump will assume that the
          filesystem does not need to be dumped.

The sixth field (fs_passno).
          This  field is used by the fsck(8) program to determine the order in which filesystem checks are done at
          reboot time.  The root filesystem should be specified with a  fs_passno  of  1,  and  other  filesystems
          should  have a fs_passno of 2.  Filesystems within a drive will be checked sequentially, but filesystems
          on different drives will be checked at the same time to utilize parallelism available in  the  hardware.
          If  the  sixth  field  is not present or zero, a value of zero is returned and fsck will assume that the
          filesystem does not need to be checked.