Use High Quality Drives
“Enterprise” class drives, typically with SCSI or Fibre channel interfaces, are tested more thoroughly at the factory (and have longer warranties to prove it). The problem is these drives are significantly more expensive than consumer drives, use interfaces most home users don’t have (SCSI or FC), and typically have much lower capacities (I don’t think anyone even makes an enterprise class drive greater than 160GB).
Better enclosures, with built-in fans are a good idea. Even better is to stick with internal drives and make sure your PC chassis has a fan or set of fans dedicated to the drives.
Think hard about “drives“ that contain multiple drives like the LaCie Bigger Disk.