What is the easiest method of checking SMART status for your hard drive?

I think "S.M.A.R.T. Monitoring tools" is the one I've used before. They give you all the parameters.

If you are going to be fooling with SMART, I'd recommend looking at the Google paper on drive failures. They are one of the few groups on the planet that have enough drives to do any real analysis, so their comments on the usefulness of SMART are probably the best research you'll find on the subject.

I like the free version of HD Tune.

From the website:

HD Tune is a Hard Disk utility which has the following functions:

* Benchmark: measures the performance
* Info: shows detailed information
* Health: checks the health status by using SMART
* Error Scan: scans the surface for errors
* Temperature display

HD Tune may also work with other storage devices such as memory cards, USB sticks, iPods, etc.

I use SMARTReporter on my Mac to put an icon in the menu bar. As long as it's green I feel OK.

SMARTReporter is a free application for Mac OS X that can warn you of some hard disk drive failures before they actually happen! It does so by periodically polling the S.M.A.R.T. status of your hard disk drive. S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) is a technology built into most modern hard disk drives that acts as an "early warning system" for pending hard disk drive problems. SMARTReporter can notify you of impending hard disk drive failures by sending e-mails, displaying a warning dialog or executing an application. The current status of your hard disk drives is always displayed through the customizable menu item.

Because SMARTReporter relies on the S.M.A.R.T. implementation of Mac OS X, it only supports ATA, SATA or eSATA hard disk drives, if you want S.M.A.R.T. support for your SCSI or FireWire hard disk drive, send feedback to Apple. Please note that a S.M.A.R.T. alert doesn't mean that your HDD will completely fail for sure, nor can S.M.A.R.T. catch all possible HDD errors - it's just a very valuable indicator.