Relax Justin. Yes, we are here to help each other, or at least we should be. Cannibusguru is probably just clowning or he's new or stoned so don't take offense every time one of these jokers make a mindless comment or you'll end up in therapy.
For the last year I've been using a progressive light schedule my instructor recommended so there's no need to go from vegging to flowering in one big step. I do it very gradually, an hour a week.
I used to do it like this: I generally went by the size and age of the plants because by the time my plants started to stink I'd usually find pre-flowers forming and that was my signal to go to 12/12. It's a hard thing to describe in text so I'd suggest that you pick up a copy of Cervantes's, "MARIJUANA HORTICULTURE the indoor/outdoor Medical Grower's Bible." You can get it from Barnes and Noble for $30 or sometimes a little cheaper on line from sources like: Amazon or Ebay.com. Of course by the time you get it you might not need it for this question. He's got good photography and an excellent explanation in chapter four which starts on page 61 and goes through page 74. He's a good reference to have on hand because of the time lapse you might have before someone has the time to respond to your question. I hope this helps.