tinmanfoto-
Ah, yes. THAT question. Time was Apple was just not tellin'. I got my cert about 5 years ago. Used to be that one had to be employed by an Apple Authorized Service Provider or Self Service Provider. Apparently, you still do. The iservices training (I am in the middle of it) is pretty vital for any Mac Tech Professional- if for noting else, the certs help you get employed- but they are not specifically Technician training- they are more systems administrator training.
So, to get Apple Authorized Technician training, I am pretty sure one still needs to be employed by a service provider or self service provider (as in a school which has its own technicians on hand- that's how I did it). You then are added to the Service Source account of that provider. Training tools are made available to you and then you just take the exams at any Sylvan site. Of course, you could just go ahead and take the exams if you are confident in your abilities. Just knowing how to swap ram or a hard drive or replace a logic board is not enough, though. Theory of Operations, Troubleshooting theory are all on the exams (or were when I took them). The exam is not so particulary interested in your vast umplummed depths of knowledge of the guts of the Mac (though that is, of course, important), but whether or not you know how to go about diagnosing a problem, finding answers, fixing the issue and dealing with the Apple related administrative stuff (AppleOrder- SROs and SSOs). When I took the exams, there were three: PowerMac, PowerBook and Printer. Now I think there's just PowerMac and PowerBook. Included are (or were... I cannot imagine they've changed all that much) sections on OS (I do not know if X is included yet), Hardware, Troubleshooting, ToO and peripherals. I will say that I would not have done well on these exams (despite a few years experience) had I not had the Apple Training. It is good stuff.
Shoot me an email if I can help any further.