(these are not hypothetical or uncommon — I've personally experienced failures related to almost all of these)

• Basic handling (fully enclosed external drives)
  
  
  • Never move the drive while it's on. When a drive is off, the heads are automatically parked and therefore protected. When the platters are moving, however, the heads are MIND BOGGLINGLY close to the surface of the drive, and head crashes can throw up particles which cause more and more head crashes to happen in the future.
  • Always put an external hard drive in a position that coworkers can't grab at them. (e.g. place your body in between the drive and the coworker) Some people aren't careful enough around hard drives, and will carelessly pick up a drive while it's spinning. It's like a gun — you, the operator, have to be personally responsible for it while it's loaded, regardless of what other people might do.
• Basic handling (bare drives)
  
  
  • When moving it from place to place, ALWAYS hold it by the sides of the drive. Holding it by the PCB risks static shock. Putting pressure on the thin housing on top of the drive can definitely cause problems. (I've done this while it's spinning — it created BAD sounds, let me tell you)
  • Never let coworkers borrow bare hard drives unless they've clearly demonstrated that they understand these rules. Don't just assume they know them.
    If they must borrow them, and they haven't clearly demonstrated competence, then you have to escort the drive to their cube and you have to be the one to attach it and oversee it.
• Use a journaling file system (e.g. NTFS, ext3). This is the only bullet-proof way to prevent the dreaded delayed write failed issue. Note that ghost.exe will gladly read/write to a NTFS partition even though it booted from a FAT partition.
• For drives you really care about (backup drives, etc):
  
  
  • Attach them inside a rigid case (i.e. a desktop) — carrying them around adds too much risk, unless they're really properly shock-protected. Use a network to physically move the data around instead.
  • If they're inside a 3.5" USB enclosure, MAKE SURE it has a fan. Modern hard drives generate a surprising amount of heat.
  • Never ever ever use important drives in bare form. This should be reserved for less important working-copies only.