Having analog inputs and outputs (often these are shared on smaller camcorders) allows you to transfer your old analog tapes to a digital format. In addition, it allows you to make copies of your digital tapes to share with others.

This is a digital interface that allows you to transfer your footage to or from your computer without first converting it to analog. In addition, a firewire cable allows your computer to take control of your camorder during this process so you don't have to fumble with tiny controls. This connection works much better for video than USB.

If your video camera also takes still photos, you'll want a USB port for easy transfer to your computer.

To ensure you are getting the audio you intended, you'll want to use headphones to listen to it while you are recording. Having a headphone jack also makes it easy for you to listen to what you've already recorded.

For those times when good audio is crucial (weddings, for example), you'll want an external microphone. No built-in microphone can match the sound of a descent external mic. In order to connect one, you'll need a microphone jack.