Hi mate,
Firstly it depends what size you wish to print - as you'll need around 6MP for A4 boarderless (going too high will just cause 'pixel noise' and actually reduce the quality).
Optical zoom over digital - always. Digital zoom is just the microprocessor blowing the image up and will proberbly lose some of the detail. Optical is actually the lens magnifying it.
The cards? Sonys, Fuji, Olympus tend to use different cards which can be more expensive. Panasonic, Canon (Same company), Samsung, Kodak etc tend to use SD.
SD & SDHC; SDHC is a new format designed for bigger cards as normal SD will hold up to 2gb. A SDHC camera can use both, but a SD camera can only use SD cards. Beward as they look the same and are the same size.
Pictbridge; this allows you to connect straight to a printer without removing the card.
Facial tracking: This allows the camera to detect faces and focus on them. Also known as 'facial detection'.
USB 1.1 or USB 2.0; not all cameras are USB 2.0 and is it high speed or full speed?
ISO: this allows the camera to compensate for low levels of light; higher the better generally.
My own camera is a Canon Ixus 7.2 MP SDHC with a 4GB card - fantastic!
Dazza :cool: