Congratulations!!!! You've decided that it's time to back up your laptop and you want to purchase an external hard drive. If you've shopped at Best Buy/Staples/Costco or any place like that, you can easily see that there is no lack of selection when it comes to hard drives so it can easily become a "What should I buy?" moment. There are many choices involved in this purchase, so we thought we'd offer some general guidelines:Connection: There are several choices of ways to connect your laptop to your external hard drive. The one you really want is USB. The "U" stands for "Universal" and it's exactly that. There is not one laptop which we've issued that does not have at least one USB port. You want that. You can get additional types of connections and even get wireless if you'd like to put it on your home network and back up wirelessly. It's your call.Capacity: There's more choices for this than there are for connection type but it depends on what you're backing up. Naturally, if you're backing up a lot of files, you want a larger (as in capacity) external drive. If you're backing up music, movies and/or photos, you reallllly want a hard drive with a larger capacity. Photos, especially those taken with a newer camera (think 12 Megapixels or larger) can be huge. If you're planning on backing up not on your work computer but your home computer (yes, you should back that up too - it's "mortal" and probably contains many important or irreplaceable files), allow some extra space. Using Apple's Time Machine to back up? It's recommended that you have an external hard drive at least twice the size of your internal hard drive. Memory has become relatively inexpensive these days so if you can swing the cost of a 1 TB (terrabyte) drive, it should last you quite some time and even allow you to share some of your space with others.Brand: We took a rather unscientific poll in the office one day and found out that we generally stick to one or two brands of hard drives until we get burned by a brand. Right now, our two favorite brands are Western Digital (the MyBook and MyPassport models are among our favorites) and Seagate Backup Plus. If you've had happy experiences with another brand, we are happy as long as you're happy...and backing up. Here are two screenshots of what is out there so you can familiarize yourself with the variety.There's one thing you do not need to concern yourself with when purchasing an external hard drive for your Mac laptop. It does NOT need to be "Mac Compatible." In spite of all of the magic that is Apple, their hard drives do not spin in a different direction or write your data in hieroglyphics. If you purchase a hard drive and get a message that the computer cannot read it, you will probably be offered an option to initialize the drive. If you don't see that option, your Mac already has the software to reformat the drive; it's called Disk Utility which you can easily find using Spotlight (the magnifying glass in the upper right hand corner of your screen). You would simply launch the utility and select the "Erase" tab and reformat your drive.