Knitting

inchainz  and I have been discussing this randomly, and I've been searching for an answer in all my knitting books, but I haven't found one.  So I come here, to the knitting group, fount of all wisdom re: knitting, and I ask:

When purling, if the first leg of the stitch is behind the needle, do you go through that instead, or do you always default to the leg that's in front of the needle?  Seems to me it would make things twist funny.  I know when I knit, I go through the first leg, front or back.  Purling front leg only can also result in a twist, so ...

Yeah, okay.  This is probably a really stupid question.  But it's itching at me!  Anyone have any wisdom to share?