He said he didn't because he was conscripted in the wardens before doing the ritual.
Yeah, but since then the canon has been retconned several times, and the official canon stance now is that Alistair did take lyrium as a Templar. He wasn't using lyrium in Origins because he'd just left the Order and still had enough residual lyrium in his blood that he could draw from to summon his abilities, but by the time the comics happen (8 years after Origins) enough time has passed that he has started taking lyrium again to use his abilities in full.
(Gives you a whole new spin on Alistair by the time of Inquisition, doesn't it? In 9:41 he's not only dealing with an aging taint and hearing the false Calling, but also with the effects of recently using/quitting lyrium again. Eesh.)
Ah, yes, I remember this now. I guess since it's part of the templar spec, it must be standard, right? I guess it stands to reason it would involve some sort of significant ritual at the start. Weird that merely being touched by lyrium would make you crave it. I wonder if it was partially being metaphorical.
I don't think it's simply being touched by the lyrium, but like, actually branded? At least I read that passage as something very aggressive, like they were burning the lyrium into the recruit (with the use of a glove and everything), forcing into the person's system. I visualize the lyrium entering the body like something out of a horror movie, like the black oil in X-Files, you know?
How can Cassandra have the same Templar skills as a templar but without taking lyrium?
Spoilers! This is explained in Cassandra's personal quest in Inquisition, so if you haven't done that yet, she'll tell you herself soon. 