Whether you call them flash drives, thumb drives, or usb keys, storage devices with flash memory are currently the most efficient, most versatile means of storing and transporting computer data. Offering true plug-and-play functionality, the drives allow you to take large amounts of data on the road without worrying about whether the computer on the other end will be able to read your data.

When shopping for a flash drive, consumers are faced with an overwhelming variety of choices. Over the last year, dozens of manufacturers have gotten into the game, offering ever-smaller devices, with ever expanding storage capacity. Drives as small as a stick of gum now offer hundreds of megabytes -- even gigabytes of storage. And prices continue to fall.

With so many devices on the shelves, its no wonder that people are confused. Worse, there seems to be little practical advice available. As a result, I regularly find myself advising my colleagues, on which devices they should buy.

The main difference in the flash drives is in the price and storage capacity. There also are some secondary considerations surrounding additional features.

The first thing you need to do is to figure out what kind of storage capacity you're going to need. If you are going to tote a few Word files, for example, you probably won't need very much in the way of storage a 128MB stick will be plenty. But if you're going to carry a lot of pictures or graphics files, you're going to need much more capacity 512MB, or more.

I have a couple of fairly large (513mb) sticks that I use to transport the PowerPoint files I use in my classes. The individual files tend to be very large because of the large number of images that I use in those slideshows. I also have a 32MB stick that I use to hold all the worksheets and handouts for all of my classes for both semesters.

In general, though, more is better. You will never be disappointed at having too much space -- only in not having enough.

Be sure that the drive is designed for USB 2.0, but is backwards compatible. Many older computers (such as the ones at my school) have only USB 1.1 ports. The safest thing to do is to have one that covers all of your bases.

Another consideration is the physical size of the stick. The general thought seems to be that smaller is better. But smaller also means that it's easier to lose. I personally shy away from the very tiny ones.

The shape of the flash drive also needs to be considered. Most of the drives are rectangular, but a few look like a lipstick, or are bullet shaped, or have other unique designs. While a different design may help the manufacturer distinguish his products, consumers need to be sure that the drive actually will fit into the available USB ports on the computers they want to use.

The peculiar angled design of the front usb ports on the computers used at my school means that only a long, narrow flash drive will fit. Any other shape requires the user to poke around on the back of the machine. The ports on the back also have the unfortunate characteristic of being too tightly spaced, so round drives cannot be plugged in at the same time as the usb printer cable.

You also should pay attention to the design of the cap that covers the USB plug on the drive. Many are attached to the drive with a small string (a good idea). Other flash drives come with a spare. I am constantly losing my caps, and the spares come in handy. Some of the newer drives have retractable USB plugs, or swivel designs that eliminate the need for a cap entirely.

Durability and reliability are also considerations. While I have never had a flash drive fail, I know that they can. Thus, I tend to stick with name brand manufacturers. While you can get a very cheap drive from an unknown producer, it may not be worth the risk.

If security is an issue, many of the manufacturers provide software that allow you to password protect your flash drive. In most of these, you can designate separate areas of your drive as "public" and "private." Others offer flash drives with biometric security features (they actually read your fingerprints).

Whether you need the security depends upon your level of paranioa. I have never used the password feature on my flash drives, and don't take the feature into consideration.

A recent trend is to offer drives with additional (and to my mind useless) features such as built-in MP3 players and voice recorders. Don't bother paying for these features. If you want an MP3 player, buy an MP3 player. You'll be much happier with the sound quality and ease of use on a device built for the task.

Finally, don't get caught up in the manufacturer's hype. My colleagues will often show me an ad and point out that a particular drive is "fast" and "multimedia compatible."

They're all fast. (And if one is faster than another, its undetectable by anyone other than the geekiest of humans) And they all can store photos, graphics and movies (assuming you have enough storage space). Anything that you can store on a computer, you can store on a flash drive.

In general, the best prices that you're going to get are online. I recommend looking at a couple of likely suspects at your local office supply mega-mart, and then going online to compare prices.