Step One: Make sure everything is backed up
There's nothing worse than nuking the hard drive on a computer and then realizing that you've just destroyed irreplaceable photos, documents, or recordings. Even if you're using Time Machine to back up your Mac onto an external hard disk drive, I recommend going through your important directories -- Applications, Documents, Downloads, Photos, Music, and Movies -- to make sure that everything has either been migrated to your new Mac or is available from a backup. I'm so paranoid that I usually keep the Time Machine backup and a secondary backup (usually made with Carbon Copy Cloner or SuperDuper!) for a while, even after I've switched machines.
Click the Read More link to learn more about how to get that old Mac ready for sale.
Photo by Flickr user sfllaw, licensed under Creative Commons
Step Two: Make sure your new machine is running smoothly
I've had friends who have basically sold their old Macs before they've even thought about buying another one. I recommend that you purchase the new Mac first, get it set up the way you want and transfer all of the data to it (either over file sharing or using the Migration Assistant found in the Utilities folder), and give yourself a week or two to make sure that your new machine isn't going to experience the heartbreak of infant mortality. Think about everything you've used your Mac for in the past, and make sure that any application you might ever need is either loaded onto the new Mac or can be downloaded and re-licensed quickly.
Step Three: Deauthorize iTunes (Optional)
If you have more than one computer, you might want to deauthorize iTunes on the old machine that you're about to get rid of. It's not that anybody is going to be able to buy music or listen to your music, since we'll take care of that in the next step. Instead, this makes sure that you don't accidentally bump up against the limit of five computers that can play your iTunes Store purchases.
Step Four: Nuke it from orbit, it's the only way to be sure
Here, I'm talking about erasing your hard drive. You never know where it's going to end up, so you want to make darn sure none of your personal information is retrievable. The best way to do this is to boot from a Mac OS X installer DVD, go to the Utilities menu when the installer comes up, and select Disk Utility. Select the drive (usually given the horribly unoriginal name of Macintosh HD), and then click on the Erase tab of Disk Utility.
Before you click the Erase button, I suggest that you click the nearby Security Options button. Here you have a couple of options, each of which is progressively more secure than the previous. My personal choice is always the 7-pass erase, which (as you can see in the screenshot below) meets the US Department of Defense 5220-22M standard for securely erasing magnetic media by erasing the drive index files and writing over the data seven times. Note that overwriting data actually hasn't been in the standard since 2007 -- the DOD now requires degaussing or physical destruction of drives -- so Apple is a bit behind the times. The overwriting process takes a while -- it often takes eight or more hours to do a 7-pass erase on a 250 GB drive. If you're really paranoid and have a lot of time, why not do a 35-pass erase?
Step Five: Reload
If you're giving the Mac away or selling it, then you probably want to reload the OS at this point. If you took my advice in Step Three and booted the computer from an OS X installer DVD, then you can just go ahead and reinstall the OS as soon as your drive erasure is complete. When the installer is done and reboots the Mac, playing variations on a theme of "Exodus Honey" by Honeycut (iTunes link), don't start going through the Setup Assistant. Instead, when you see the startup screen, just use Command-Q to quit the installer. Eject the DVD, and shut the computer down. The next time it is started up, the new owner / user will get to go through all of the joy of setting up the Mac.
Step Six: Clean it up
Maybe it's just me, but I don't like the thought of sending someone a computer if it has fingerprints, smears, and cruft on the keyboard and mouse. So what do I do? Unplug everything, grab a microfiber cloth lightly dampened with water and give the computer a once over. At least it's going to be somewhat cleaner than it probably was. If you have one of the older keyboards, turn the sucker upside down and give it a good shake to get food crumbs, boogers, cat hair, and dust out of the spaces between the keys. Even better, use a vacuum with a soft brush attachment to clean the keyboard. Any remaining fingerprints or smears might need a touch up with iKlear or a similar spray.
Step Seven: It's picture day! (Optional)
When I sell something on eBay, I always try to take a bunch of photos of the actual merchandise instead of just using a generic picture. Why? It shows people exactly what they're going to get. If they see that the Mac I'm selling them really looks pretty good and comes with an extended keyboard and all of the original paperwork, they usually trust that the machine has been taken care of during its life with me. That usually ends up resulting in higher bids, although your mileage may vary. I like to take the photos with the original packaging, cables, disks and manuals in view.
Step Eight: Put it back in the box
You did keep the original packaging, didn't you? Well, if you did, you're in good shape because the original Apple packaging is designed to keep your Mac safe during shipping. Make an attempt at putting it back into the box, plastic, wrapping paper, or whatever came with the computer, and it should be ready to go. If you don't keep boxes (many people don't due to lack of space), then be sure to package the Mac well. One of the best, albeit expensive, ways to do this is just to take the Mac to a UPS or FedEx store and have them package it for you.
Apple has a pretty decent recycling program -- if your old Mac or PC still has monetary value, they'll send you an Apple Gift Card for the amount through a program run by PowerOn. If it doesn't, they will "recycle it responsibly" for you. You can purchase a prepaid shipping label for $30, slap it on the box, and rest assured that the Mac isn't going to be sent to a hazardous third-world recycling plant.
Gazelle.com purchases used equipment in good condition, although often the proceeds are less than what you'd get from an online auction. The company believes that recycling begins with reuse, so they will buy or take your equipment and resell it. They've also set up a network of recyclers across the U.S. if your product is too old to sell, and I was surprised to learn that most Office Depot stores will accept electronics for recycling.
Do you have any favorite hints for getting your old Mac or other electronics ready to be reused or recycled? Let us know in the comments.