Hardware
“Design for one hand whenever possible. Take advantage of hardware buttons (start, back, and search). Gestures available: tap, double tap, touch & hold, pan, flick, pinch & stretch. Touch: recommended touch target size is 9mm. Minimum touch target size if 7mm. Minimum spacing between targets is 2mm. Visual size is 60-100% of the touch target size.” – Microsoft, via Luke Wroblewski