Design Memory capacity

Unless you are a budget buyer, you should probably forget about players with less than 512MB of onboard memory. These days considering the cost of these players, 1GB should be within most people's reach (these can be found for under $100).

Of course, you always have the option of increasing the amount of music you can fit per megabyte by upping the compression, but bear in mind this may involve time-consuming re-encoding of your MP3 files as well as loss of quality.

Interface and navigation

Some ultra-portables keep the size and weight down by omitting a display altogether - the iPod Shuffle is a good example of this. This is fine if you're not too fussy about navigating around your files but can be an outright pain if you're picky.

Some models make a good compromise by incorporating flashing LED lights or a small OLED display that give you some feedback on play mode, battery life and other basic settings. Others have a backlit LCD that can be great in low light, but they use a little extra battery power.

If you want to know all the details of each track, the file's bit-rate, the playback position, battery usage and equaliser settings, then you'll need a multi-line display. Otherwise, a single-line LCD will probably do.

Small, multi-line LCD displays can sometimes display scrolling text based on an MP3 file's ID3 tags (information about which song, artist, album etc is playing). It's worth pointing out however, that some smaller players don't scroll text and can only show 32 characters - this may or may not be a concern for you.

Also note that some MP3 players have wired remote controls (often with LCD displays) that go between the player itself and the headphones. Either way, always try and have a tinker with a prospective player to see how intuitive its interface is.

Generally, the bigger the display on your MP3 player, the easier it will be to navigate. That said one common complaint is that it's usually a challenge to search through gigabytes of songs. Try to create a track playlist within the device (which isn't always possible) and check to see if there's smart (automatic) playlist creation. This might or might not be based on songs you haven't listened to in a while - or on certain music genres.

Pay really close attention to the interface - you're going to be using it, so you may as well choose a player with a navigation method you not only understand but actually like!