The preview will be available to the first million people who sign up for the The OS X Beta Program. Users will be able to test-drive pre-release versions and let Apple know what they think.
The public beta version of OS X Yosemite is the same version released to developers on Monday, so to start off, consumers and developers will be running the same software. However, the developer version of Yosemite will be updated more often over the next few months than the public beta version. This is so developers can continue to test their software with the latest operating system available. Consumers really don’t need updates that frequently.
You can sign up for the Beta Program at the link below...