Go into the App Store application and open the Purchases tab at the top of the screen. This is a simple but slightly time-consuming process. Unfortunately, the file you download from the Mac App Store to your computer deletes itself after you update to Lion, so you’ll probably need to redownload the OS update. The first step in getting Lion onto your USB drive is to obtain a copy of the OS itself. All you need is a few minutes, a copy of Lion, and a USB flash drive with at least 4GB of storage (though more is preferable). With Mac OS X Lion and a new piece of free software, it’s easier than ever to create a USB keychain that you can boot from. It’s also extremely useful for keeping your basic setup consistent across multiple computers, if you find yourself switching hardware regularly and I’ve had fun in the past setting up a bootable USB keychain loaded with all the apps and files I need to turn any Mac-compatible computer into a viable media center quickly and easily. A bootable Mac OS X thumb drive comes in handy when you need to troubleshoot OS issues for yourself, your family, or your friends.
