I initially created an Image for my Win 8 OS as I always do when I am loading a new OS. This allowed me to restore Win 8 easily if things did not work out with Win 8.1.
I then downloaded the Win 8 ISO file to my PC. I did not burn a DVD at this time. I always can do that later, and I figured why waste a DVD if I do not have to. Next I started the installation and chose to keep everything.
When the installation completed I started my customization. First there were a few updates from WU. Next I had a few things that had to be reinstalled. AVG 2014 beta was installed and took over automatically from Windows Defender. Next LastPass had to be installed (it did not carry over, I suspect because of the new IE 11. I had to turn off Enhanced Protection Mode). I also heard of a beta version of Start8 beta. This can only be downloaded by those registered Start8 users. It worked flawlessly. I knew it would not be long before these Start Menu add-on apps were updated for Win 8.1. I also had to reinstall my printer driver.
Once I had everything customized properly and to my satisfaction, I defragged the entire setup then created an Image of this new OS with my Acronis TI boot disk. Once I had the image, I restarted and booted into Win 8.
I then used Partition Wizard mini-tool to create a new partition at the end of my data partition. I set it to about 40 GB. I formatted it to Logical NTFS drive. I then rebooted to my Acronis TI boot disk and restored my Win 8.1 Image to this new partition. Some would think I was done at this point, but not so.
Because Win 8.1 was not installed, just restored from an Image, I had to once again boot into Win 8 and use EasyBCD to add Win 8.1 to my Boot Record. This allows my PC to see both Win 8 and Win 8.1 OSes when I boot. Without this step, when I booted, my PC only saw the Win 8 partition.
Now when I boot, I am given the choice of which OS I wish to boot to, nice!
I also have a separate Data Partition. Since I installed Win 8.1 directly over Win 8 initially, all my data pointers were still pointed to the Data Drive. Now whether I boot to Win 8 or Win 8.1, everything still points to the same data folders on my Data Partition, nice!
I know this seems a rather lot to go through to set up a dual boot, but it really was not, and allows me more flexibility to test Win 8.1 easily.