Simply go ahead and upgrade your Mac to Yosemite through the App Store. Yes, we will take a step back to take two steps forward. No tricks needed! Step 1 – Update to Yosemite! You can do all of this using standard options.
This will allow you to then boot from the USB drive and make it possible for you to unmount your computer’s internal drive, format it and install Yosemite on it from the USB drive. Use the new Recovery Tool from your updated Mac to install Yosemite on a USB drive. The strategy is to upgrade the OS on your computer as intended by Apple through the App Store. My Mac is constantly being backed up to a NAS device, hence I take this for granted, but this is an important step. Important: Backup all the data that you need.Make sure you have a fast and, more importantly, a reliable internet connection.Make sure your Mac is connected to a power source.
Time – I ended up watching two prime time show episodes while doing this!.A Mac that can actually upgrade to OS X Yosemite.A USB flash drive with at least 16 GB space.There is a much easier way using only standard options. Most guides out there to clean install the OS involve some command line gymnastics and tricks involving downloading the update and not running it etc. This has become harder as Apple has started to release their OS through the App Store as an update only.
Whenever a new version of OS X is released, I use it as an excuse to rejuvenate my system by doing a clean install.