1. Smooth multi-point camerawork using a proper video camera - no substandard mobile phone footage.
2. Participants who are clearly fond of each other and used to playing together.
3. No looking at the camera!
4. Plenty of anticipation - after all, what you can't quite see is the most enticing!
5. No un-necessary dialogue, scene-setting or script, which usually does nothing other than amplify poor acting skills.
6. Points of view to illustrate the spanker's and the spankee's perspective - facial expressions, etc.
7. Minimal use of slow motion.
8. 5 minute maximum length.
Any other ideas?