On PC's and laptops running an older OS, this is just a simple matter of going into the BIOS and setting the boot sequence and putting the boot cd/dvd in the drive. In many cases you can even just hit one of the F* function keys to bring up the boot sequence menu on-the-fly during POST.
The main problem I'm running into is that other devices besides the primary HD is disabled when SecureBoot is enabled. So far the only way I've gotten it to work is to disable SecureBoot and enable something called legacy mode.
Needless to say this make it difficult to boot things like OS recovery tools, PartitionHD backups, Linux LiveCD's and a bunch of others. Is there another procedure for doing this since it seems to mess up the Windows 8 install? By mess up I mean that after re-enabling SecureBoot and starting Windows 8 normally, the OS goes into a 'preping repair phase' for some reason that takes forever to complete before getting into a usable desktop.