For me, it depends on what I'm doing at the moment when I begin to feel the pill...
1) Standing/walking - I usually get a slight head rush, not unlike being high... then it almost feels like im falling forward very slowly.
2) Sitting - I feel the head rush more slightly than when I'm standing up, and I don't get the falling feeling.
Usually always I can tell because I begin to breath a bit deeper and my jaw goes nizutz.
SOmetimes I get delayed vision, not hammer-vision... Like when yur drunk and you turn your head it almost seems like your eyes are following your head.
-Eo