If you have an OS X developer account, and want to work with OS X 10.9 Mavericks, you may prefer to do so using a virtual machine, in Parallels Desktop or VMware Fusion. However, you won’t be able to create a new virtual machine in either of these programs using the Mavericks installer.
John Martellaro, on The Mac Observer, posted an article with links to Parallels knowledge base articles explaining how to do this. You’ll need to update Parallels Desktop, then create a snapshot of an existing virtual machine and install Mavericks on that.
For VMware Fusion, the process is quite simple: take an existing virtual machine, running 10.7 or 10.8, duplicate it in the Finder, then launch VMware Fusion. Choose File > Open, then select the duplicate virtual machine. Rename it, then launch it. Fusion will ask if you moved or copied the virtual machine; click I copied it.
After you’ve launched the duplicated virtual machine, run the Mavericks installer from within that virtual machine.