About RevoStick and RevoDisk

RevoStick
Let's first start by telling what a RevoStick is. A RevoStick is a simple USB Flash Drive, setup in a special way to boot OS X. RevoStick's are mostly used as rescue booters, but can easily be used to test drive a new OS version or certain drivers / OS settings. All this without breaking your working setup.

RevoDisk
There's also RevoDisk. This takes it one step further, by using the same kind of setup, but here we use a 60GB OCZ Agility 3 Series SSD. Please note that the brand / type doesn't really matter, but this is an inexpensive SSD and it suits us well for this purpose. Very well even.

The Setup
You need to copy a number of files and create some directories to setup a RevoStick / RevoDisk, which we'll explain here for you:

/boot
/Extra/ACPI/ssdt.aml
/mach_kernel
/System/Library/Caches/com.apple.kext.caches/Startup/*
/System/Library/Extensions/*
/Library/Preferences/SystemConfiguration/com.apple.Boot.plist

Note
RevoBoot checks the first hard drive to see if it can boot from it, but you can also add a target UUID (rd=uuid boot-uuid=) in com.apple.Boot.plist to boot from the specified UUID (aka hard drive/partition). This enables you to boot from say the Recovery HD on your hard drive, but you have to make it work for your setup.

The trick here is that we load the kernelcache and/or kexts from the RevoStick/RevoDrive instead of the hard drive. Also. You are advised to boot in verbose mode (-v) when you boot from a RevoStick since booting from a RevoStick usually takes a lot longer, but that doesn't really matter when your OS X installation refuses to boot. Think rescue mode. Sort of a last resort before having to reinstall OS X.