Signs you've taken a good hit:

[Matt the Funk]

you cant blow out the hit in one breath...
by the way, nice av dude.. haha

Exactly. I make sure all my hits are fat. Empty out the lungs and take in full smoke(may make you kinda lightheaded, but I think you get the most outta your weed) and you should be exahling in atleast two breathes.Well not shouldn't, but THAT is when you know you got a good hit.