The logo will have the Apple mac 'Aqua' look (reflective glass/water), be roughly square in dimensions, and should be scalable (vector based). It should also have a scaled down icon format (57x57 pixels) and look fine at intermediate sizes (e.g. 100x100 and large: 1600x1600). Therefore vector is mandatory.
Please send as many examples as you can of logos you have designed, preferably as JPEG or PNG files. Please try to send some examples with the Apple Mac shiny "Aqua" look.