There are many good external drives, I get mine from OWC, http://www.macsales.com where they are Mac specialists. Good software is Carbon Copy Cloner and SuperDuper, both have ability to copy the internal drive and create a bootable copy of the Mac OS X for you.
Clone Lion/Mountain Lion using Restore Option of Disk Utility
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
- Select Disk Utility from the main menu then press the Continue button.
- Select the destination volume from the left side list.
- Click on the Restore tab in the DU main window.
- Check the box labeled Erase destination.
- Select the destination volume from the left side list and drag it to the Destination entry field.
- Select the source volume from the left side list and drag it to the Source entry field.
- Double-check you got it right, then click on the Restore button.
Destination means the external backup volume. Source means the internal startup volume.
Get an external drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility as outlined above. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):
Although you can buy a complete external drive system, you can also put one together if you are so inclined. It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice. Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at Storage Review.
Enclosures for FireWire and USB are readily available. You can find only FireWire enclosures, only USB enclosures, and enclosures that feature multiple ports. I would stress getting enclosures that use the Oxford chipsets especially for Firewire drives (911, 921, 922, for example.) You can find enclosures at places such as;
All you need do is remove a case cover, mount the hard drive in the enclosure and connect the cables, then re-attach the case cover. Usually the only tool required is a small or medium Phillips screwdriver.