Not all Apple Macintosh computers come with built-in iSight web cameras. And of those that do, such as MacBook and iMac models, you don't really have much flexibility of webcam angle or placement such as you might with an external USB webcam.

Mac Pro tower and Mac mini owners, as well as older iBook and G4-era systems are most likely to be looking for webcams to add the videoconferencing abilities most other Mac owners take for granted. Most webcams compatible with Mac OSX connect via USB 2.0. But there are FireWire 1394 camera options that pro-level users may want to explore for higher frame-rates and less CPU overhead. Many FireWire enabled DV camcorders can be used as an alternate to a USB camera.

A new standard in webcams: UVC compliance - is a great help choosing and buying a Macintosh webcam easier. It is a USB 2.0 based standard, so it's critical that you have a rather recent Mac who's ports support the high speed - and high data transfer rates full-motion videochat requires. In general, any older Mac with a 1ghz G4 processor or faster came with USB2 ports. You also need to be running AT LEAST OSX 10.4.3 Tiger (ideally 10.4.11 update) or 10.5.x Leopard to take advantage of the built-in UVC webcam drivers in OS X.

Stabilize the web cam on a solid mount to prevent unwanted movement and blurring

Use TWO light sources to eliminate shadows, low frame-rates and graininess

Quit other unneeded Mac applications to eliminate CPU overhead and maximize frame rates

Beware of running other video/audio apps that may compete with your webcam or microphone.

Double-check your Audio and Video settings before establishing a connection in iChat, Skype, ISPQ or Yahoo Messenger to make sure you'll be seen AND heard

You may find your USB webcam performs better on a dedicated USB port - and not shared with a mess of other devices on a 4 or 7 port hub