I'm not sure it makes much difference whether you shave WTG top down on your face, or bottom up, just as long as you're stretching the skin in the opposite direction to hair growth. I reckon most people do this on the side of their face since it's the classic 'reach over' hold that you see pretty much everyone do.

However, it took me a while to realise I was stretching my skin in the wrong direction on my neck. For a while I was stretching in the direction of hair growth, mainly due to the irregular growth pattern that I have there (and many others share the same issue). Once I realised what I was doing (one of those doh! moments), I stretched my neck skin the opposite way. It made a huge difference immediately -- closer shaves, fewer passes.

Of course, some areas you can't stretch the right way (e.g. top lip). I think most people do whatever they can in that case. My own freaky technique is to simultaenously puff out my cheek and stretch the skin towards my ear. This is the sole reason I don't do a shaving video -- it makes me look like a twat.