Schottky Diode for back EMF
I need some advice choosing a suitable SMD schottky diode for my PWM
driven motor to handle back EMF.

Don't worry about it being a schottky, in fact, there are little reasons to use one because low forward volt drop is of no-importance when suppressing back emf whereas high reverse leakage current (as is often the case with a schottky diode) can be problematic in some designs.

What key parameters within a data-sheet do I need to look for to suite
my application.


Reverse voltage 1.5 x greater than maximum power supply voltage
Switching speed unimportant
Continuous current rating 1.5 x greater than stall current of motor
Power rating about 1 volt x maximum current rating (volts x amps = watts)