what do I use to back up my macbook pro?

Basic Backup

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. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

Carbon Copy Cloner

Synk Pro

Tri-Backup

Visit The XLab FAQs and read the FAQ on backup and restore. Also read How to Back Up and Restore Your Files.

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;

Cool Drives

OWC

WiebeTech

Firewire Direct

California Drives

NewEgg

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.

Clone using Restore Option of Disk Utility

1. Open Disk Utility from the Utilities folder.
2. Select the destination volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Check the box labeled Erase destination.
5. Select the destination volume from the left side list and drag it to the Destination entry field.
6. Select the source volume from the left side list and drag it to the Source entry field.
7. Double-check you got it right, then click on the Restore button.

Destination means the external backup drive. Source means the internal startup drive.

Some reading by one of the senior contributors to the forum: https://discussions.apple.com/docs/DOC-3045

I use an external drive, Firewire because it is faster.

As described in the article, I use a clone product ... CarbonCopyClone. It makes an *bootable* image of the current startup partition that can be moved back onto any new target drive, and can be used to start the system because it is bootable.

But read the article (quickly) to decide for yourself.

You might want to review the Time Machine Tutorial, and perhaps browse Time Machine - Frequently Asked Questions.

See Time Machine vs. Clones and Archives for an overview of the different types of backup apps, the advantages and disadvantages of each, and some recommendations.