More Mac 101, our tips and tricks for novice Mac users.
Update: You cannot install Snow Leopard on an 8 GB flash drive. I was incorrect in writing that an install of Essential System Software would take 3.81 GB. As a few of our commenters pointed out, and as is the case, in testing I erroneously tried to install Snow Leopard on a flash drive that already had a version of OSX on it, making the installation much smaller than installing on an empty flash drive. According to readers, installing Snow Leopard on an empty flash drive will take 8.01 GB requiring a 16 GB flash drive. I'm very sorry for any inconvenience this has caused.
It's a good idea to have a strategy in place in case of emergencies. If your hard drive tosses you errors, behaves badly or doesn't even appear, what to do? If programs crash at random, you need to be ready. You can prepare for this by creating a bootable flash drive containing some diagnostic and repair utilities.
This is not meant to replace or in any way affect backing up your hard drive. Time Machine makes it so easy that not having a backup plan is just silly... but so much for the disclaimer.
To make a diagnostic and repair flash drive, I'd suggest buying an
8 GB flash drive, 16 GB flash drive which can be had for around US $20 US $35 these days. When you get it, it probably won't be formatted for your Macintosh, so plug it in and run Disk Utility (in /Applications/Utilities) to format the flash drive. In doing so, you have a number of choices. With your flash drive highlighted click on Erase and choose Mac OS Extended (Journaled) and give the flash drive a name. Then click on Erase on the bottom right side of the screen and in a few seconds your flash drive will be ready for an operating system.
I inadvertently omitted a step! Click the icon for the drive (not the disk partition -- the one that includes the size) and click the Partition tab. Choose "1 Partition" from the pop-up menu, Mac OS Extended on the right, then click Options at the bottom of the screen and make sure "GUID" is the selected partition type. Thanks to everyone who pointed this out.