when i'm sitting, i tend to be aware if i slouch or foot falls asleep or jaw is tight, i was never taught it as any formal meditation though.
and to AdvaitaJ, i do something similar but i'll note hardness, cold, etc where hands are on the wheel or but is on the seat, wind hits legs that sort of thing, try to see it for what it is, sound as sound not song or voice etc. hearing as hearing that sort of thing.
สัพเพ สัตตา สุขีตา โหนตุ
the mountain may be heavy in and of itself, but if you're not trying to carry it it's not heavy to you- Ajaan Suwat