How does one get approached by agencys to start shooting for them? any help along this would be appreciated!

I don't think an agency will approach you, you have to approach an agency.  I haven't heard of a case where agencies are the ones scoping for their stylists, unless they are far beyond qualified, I would say.  But who knows, anything can happen.

What you could also do is call any local modeling agencies and ask to test with their newly signed models.  Yeah, it's TFP and TFP sucks, BUT you get good pictures, with good models and you just might turn out to be their top pick for a stylist and you know word of mouth is BIG and the rest might turn out to be history.

Sorry, wasn't paying attention, in your case, photographer.

How do agency tests work, exactly?

I ask because I'm only familiar with Internet TFP/TFCD arrangements and I'd like to know what the agency standard rules are.

Basically, you walk in the door and ask them...Usually on the days that their open calls are scheduled for.  Or you can check their website and find who their bookers are and try to contact them directly for an appointment.  They'll want to know if you are working w/stylists and if you have a studio or not.  Then they'll look at your book, if they like what they see they'll give you a compcard of someone to test for them, in my case it was a runway model who was segwaying into the print side of things and needed a good headshot.   I think I might have gotten a little lucky because I already had 2 models that the agency represented in my book at the time and they liked what I had of them..