Download the current version (1.1) of Disk Watcher (documentation included).
Disk Watcher automates checking your disks for corruption. With Disk Watcher you don't need to remember to regularly check your disks to prevent serious problems. Disk Watcher will keep an eye on them and warn you when a disk has problems and needs to be fixed.
The disk checking itself is done by Disk First Aid - Disk Watcher takes care of the automation of it all. DiskWatcher will inform you if any disk problems are found and keeps a log of all it did. Optionally, Disk Watcher can even respond to disk errors by having custom "actions" launched. This makes Disk Watcher a very powerful tool.
The idea is 'damage prevention'. Too often people wait with running disk repair utilities until it is too late. Still fixable disk problems are ignored, new problems get stacked on top of the old ones, and finally the system breaks down and Disk First Aid can't fix it anymore. Then they have to run out and buy a disk repair utility (like DiskWarrior, TechTool Pro or Norton Disk Doctor) and can only hope that it can still fix things. In the mean time, the disk cannot be used safely.
These days, Apple's Disk First Aid is quite good at repairing problems as long as they aren't too severe. So the only thing you really need to do is run Disk First Aid on a regular basis, not waiting until you're having problems. Disk First Aid comes with the Mac OS, for free, so why not use it? Because it's too much work for most people - you need to remember to regularly launch Disk First Aid, select all the disks you want to check, and then tell Disk First Aid to check them.
With Disk Watcher you can afford to be lazy ;) You just install Disk Watcher and don't worry about disk corruption anymore. Disk Watcher will inform you when there is a problem.