Sometimes, especially when I smoke by myself, I like to try and pay attention to the actual part when I "slip" into my high, but I'm normally high before I even know it.
Like, I'll stare off and wonder...then before I know it five minutes has past and I haven't even hit the bowl again. My eye lids get lower, and my head feels lighter, but not in the fainting way.
It's just a pure feeling.
God, I love that feeling. :)