Please NoteUpgrading from 10.8.x to 10.9.x
If your OS X install uses a relatively recent version of the ProBook Installer (v6.1 or newer), then it is probably safe to upgrade directly from 10.8.5 to 10.9. You should always create a backup before attempting an upgrade on major version upgrades such as 10.8.x to 10.9.x just in case something goes wrong and you aren't able to recover.
1. If you use the 'blinkscreen' workaround for screen brightness, use the latest ProBook Installer, prior to beginning the update process to update blinkscreen to the current version. This insures you have a blinkscreen compatible with Mavericks.
2. First download Mavericks and create your Unibeast USB and launch the Mavericks installer according to the Installation section above (steps 1 through 8).
3. Since you'll be installing to an existing partition and upgrading it, do not use Disk Utility to erase your partition. Instead, select your existing partition to install Mavericks to and complete the Mavericks installation.
4. After Mavericks installs, it will restart your computer. After it restarts, you will need to once again hit Esc then F9. Then select the USB hard drive again. This time, select the partition you just installed Mavericks on, type "-f" then press enter.
5. After reaching the desktop, run the ProBook Installer, and select the "OS X support kexts" appropriate for your laptop, and the AHCI patch, if you need it. Also, if you have not used the ProBook Installer DSDT patches in a while, and you use the Atheros AR9285 for WiFi, select only the "Atheros 9285 patch" from "DSDT generator/patcher -> Optional patches." In addition, if you have not upgraded your bootloader in a while, now is a good time to upgrade to the latest Chameleon via the ProBook Installer, because otherwise you may not have a bootloader compatible with Mavericks.
6. Click continue to install your ProBook Installer choices, allow it to complete, then restart the computer.
7. If you have an SSD (Solid State Drive) and wish to enable TRIM, run Trim Enabler to turn on TRIM (it patches IOAHCIBlockStorage). Repair permissions & rebuild cache, then reboot.