This article was originally published on Computerworld.com.

For the first time since the OS X beta test of 2000, Apple is allowing Mac users to test and provide feedback on a prerelease version of OS X. The first 1 million people to sign up for the beta program through Apple’s Web page—which crashed under heavy traffic on Thursday after the public beta became available—get a redemption code to download the Yosemite beta via the Mac App Store.

Remember this? The last time Apple offered a public beta was in 2000. The preview version of the first iteration of OS X came on a disk with a handy how-to guide.

Further reading: Macworld's Yosemite FAQ and hands-on with Yosemite series

If you’re lucky enough to be one of those beta testers, congratulations! Here’s a quick rundown of what you should know and keep in mind about the beta as you start poking around Apple’s latest operating system. (The final version is due out this fall.)

1. The beta is a work in progress

First and foremost, keep in mind that this isn’t the official release of the software; Apple is still testing and tweaking Yosemite. That means it may not function as expected. Some features may be completely absent or could differ from what Apple showed off during its WWDC keynote in June—and some features may look very different in the final release. Even some of the standard features available in Mavericks or earlier versions of OS X may be missing, nonfunctional or just different. That’s because a major OS upgrade, particularly one like Yosemite that makes major changes to the user experience, often involves updating or altering existing functions, including core components that aren’t visible to most users.

2. A public beta isn’t the same as a developer preview

Apple has already released beta versions of Yosemite to members of its Mac developer program. The most recent was made available to them earlier this week, with revisions arriving roughly every two weeks. In fact, the version of Yosemite offered as the public beta has a different build number (it’s one digit higher) than the version developers received on Monday.

Apple’s FAQ for the Yosemite beta indicates that beta testers may not see updates at the same rate as developers. There’s a good chance this means beta testers will see less frequent updates than developers.

Other differences are likely to include support, resources or some functionality. Developers are receiving the betas to build and/or test apps running under Yosemite and make changes if needed. Beta testers are being asked to provide feedback. Those are rather different roles, and developers aren’t likely to provide the type of feedback—general user interface (UI) issues or consumer-oriented feature requests—that Apple is looking for from public beta testers.

3. Explore Yosemite and report back to Apple

Apple’s goal with this program is largely to solicit feedback about Yosemite, particularly about its new UI. If there are things that aren’t working, are confusing, seem like they should work better, or that you really dislike, you should report them to Apple using the Feedback Assistant that’s included. During the public beta prior to the release of OS X in 2000, Apple made several changes based on user feedback—the most obvious was restoring the Apple menu in the shipping version of OS X, which had been replaced with an Apple logo in the middle of the menu bar.

Although Apple suggests simply using your Mac as you normally would, you should also explore a bit. The advantage here for Apple is that you’ll play with more Yosemite features and potentially provide more useful feedback. You also might discover new (or existing) features that you might not have considered using otherwise.

Apple wants to hear what testers think about Yosemite via the built-in Feedback Assistant.

You should also report issues with third-party software if it seems that Yosemite has broken something in existing apps. That gives Apple the ability to look at underlying problems affecting those particular apps and potentially others.

4. Don’t install Yosemite on a mission-critical Mac

You shouldn’t install the Yosemite beta on a Mac that you need for important work. There’s a very real possibility that you may encounter a serious problem—like losing important data, having some key apps stop working or having your entire Mac be disabled.

Let me repeat: Don’t install the beta on your primary Mac—the computer you use day-in and day-out for work or personal tasks. You should install it on a secondary Mac that can easily be wiped clean and restored if need be.

5. You can install Yosemite on an alternate drive or a virtual machine

If you only have one Mac or you decide to ignore my advice and install Yosemite on your primary machine, you should at least consider putting the beta on a drive that isn’t your typical startup drive (usually the internal hard drive or SSD inside your Mac). You can install the beta on an external drive, a second internal drive (if your Mac has one), or a hard-drive partition. You can then boot from that drive or partition when you want to use the beta and boot up from your primary startup drive when you need to get things done.

Installation on an alternate drive reduces the risk that a catastrophic failure will befall you or your data, but it isn’t a guarantee. An issue that impacts your Mac’s file system could affect both the alternate “Yosemite beta” drive and your startup drive. The most likely scenario in this case would be that some type data loss that hits all data on both drives.

Another option, if you have a copy of Parallels Desktop or VMWare Fusion, is to install the Yosemite beta on a virtual machine. Although these tools are typically used to create virtual machines running Windows, they do support other operating systems, including OS X, meaning you can create a virtual Mac and install the Yosemite beta on it. That also reduces—but doesn’t entirely remove—the risk of problems. If you go this route, you’ll want to disable any features that allow the virtual machine to exchange files with your physical Mac to minimize potential data loss if there’s a file system issue.

6. Back up any Mac before installing the beta

Whatever Mac you install the Yosemite beta on, and no matter how you install it, you should ensure that you have a complete and functional backup before beginning, even if you are installing on an alternate drive or into a virtual machine. You should also perform regular backups during your testing period. And you should store a known good backup—disconnected from your Mac—while testing because a file system issue could damage the data on your backup drive. Ideally, you’ll use a second backup drive to perform any regular backups of your Mac while running the Yosemite beta.

Futher reading: Macworld's Backup basics series

7. Think carefully before using iCloud or third-party sync solutions

The Dropbox-like iCloud Drive is in OS X Yosemite, but you may want to wait until it arrives in final release form.

The risk of data loss isn’t restricted to data on your Mac: iCloud data sync among multiple Apple products and third-party cloud services like Dropbox or Google Drive allow your Mac to work with and alter data in the cloud and on other Macs, PCs or mobile devices. You should carefully consider whether you want to risk changes or loss of data maintained or synced through such services. If you decide to use them on a Mac running the beta, you should ensure you have a known good copy of that data separate from the version of the data in the cloud.

Continue reading to learn more about iCloud and Yosemite and six more things you need to know before diving into the OS X beta.